From 248e8ffa81e1a3131477185263fe77aad0316fd4 Mon Sep 17 00:00:00 2001
From: Vedanshu Jain <vedanshu.jain.2012@gmail.com>
Date: Mon, 10 Oct 2022 13:45:18 +0530
Subject: [PATCH] Revert "Revert "[COT] Add the orders cache" (#34992)"

This reverts commit 0b5d7ab9ad4ef09fc0ef47c5deddfe2aa4f7e5c3.
---
 plugins/woocommerce/changelog/add-order_cache |   4 +
 .../includes/abstracts/abstract-wc-order.php  |   7 +
 .../admin/class-wc-admin-settings.php         |   3 +
 .../includes/class-wc-order-factory.php       |  45 +++++-
 plugins/woocommerce/src/Caches/OrderCache.php |  44 ++++++
 .../src/Caches/OrderCacheController.php       | 121 ++++++++++++++++
 .../woocommerce/src/Caching/ObjectCache.php   |  74 ++++++++--
 .../Orders/CustomOrdersTableController.php    |  44 +++++-
 .../DataStores/Orders/DataSynchronizer.php    |   6 +
 .../COTMigrationServiceProvider.php           |   3 +-
 .../OrdersDataStoreServiceProvider.php        |   7 +
 .../Internal/Features/FeaturesController.php  |   5 +
 .../woocommerce/src/Utilities/OrderUtil.php   |  11 ++
 .../class-wc-rest-orders-controller-tests.php |   7 +-
 .../tests/php/src/Caching/ObjectCacheTest.php | 131 ++++++++++++++----
 15 files changed, 460 insertions(+), 52 deletions(-)
 create mode 100644 plugins/woocommerce/changelog/add-order_cache
 create mode 100644 plugins/woocommerce/src/Caches/OrderCache.php
 create mode 100644 plugins/woocommerce/src/Caches/OrderCacheController.php

diff --git a/plugins/woocommerce/changelog/add-order_cache b/plugins/woocommerce/changelog/add-order_cache
new file mode 100644
index 00000000000..1b800aff214
--- /dev/null
+++ b/plugins/woocommerce/changelog/add-order_cache
@@ -0,0 +1,4 @@
+Significance: minor
+Type: add
+
+Add a cache for orders, to use when custom order tables are enabled
diff --git a/plugins/woocommerce/includes/abstracts/abstract-wc-order.php b/plugins/woocommerce/includes/abstracts/abstract-wc-order.php
index 78932ad68bc..bebe53ada46 100644
--- a/plugins/woocommerce/includes/abstracts/abstract-wc-order.php
+++ b/plugins/woocommerce/includes/abstracts/abstract-wc-order.php
@@ -10,9 +10,11 @@
  * @package     WooCommerce\Classes
  */
 
+use Automattic\WooCommerce\Caches\OrderCache;
 use Automattic\WooCommerce\Proxies\LegacyProxy;
 use Automattic\WooCommerce\Utilities\ArrayUtil;
 use Automattic\WooCommerce\Utilities\NumberUtil;
+use Automattic\WooCommerce\Utilities\OrderUtil;
 
 defined( 'ABSPATH' ) || exit;
 
@@ -203,6 +205,11 @@ abstract class WC_Abstract_Order extends WC_Abstract_Legacy_Order {
 
 			$this->save_items();
 
+			if ( OrderUtil::orders_cache_usage_is_enabled() ) {
+				$order_cache = wc_get_container()->get( OrderCache::class );
+				$order_cache->update_if_cached( $this );
+			}
+
 			/**
 			 * Trigger action after saving to the DB.
 			 *
diff --git a/plugins/woocommerce/includes/admin/class-wc-admin-settings.php b/plugins/woocommerce/includes/admin/class-wc-admin-settings.php
index 477ae41ea61..2958d949806 100644
--- a/plugins/woocommerce/includes/admin/class-wc-admin-settings.php
+++ b/plugins/woocommerce/includes/admin/class-wc-admin-settings.php
@@ -488,6 +488,8 @@ if ( ! class_exists( 'WC_Admin_Settings', false ) ) :
 							$visibility_class[] = 'show_options_if_checked';
 						}
 
+						$must_disable = ArrayUtil::get_value_or_default( $value, 'disabled', false );
+
 						if ( ! isset( $value['checkboxgroup'] ) || 'start' === $value['checkboxgroup'] ) {
 							$has_tooltip             = isset( $value['tooltip'] ) && '' !== $value['tooltip'];
 							$tooltip_container_class = $has_tooltip ? 'with-tooltip' : '';
@@ -515,6 +517,7 @@ if ( ! class_exists( 'WC_Admin_Settings', false ) ) :
 						?>
 							<label for="<?php echo esc_attr( $value['id'] ); ?>">
 								<input
+									<?php echo $must_disable ? 'disabled' : ''; ?>
 									name="<?php echo esc_attr( $value['field_name'] ); ?>"
 									id="<?php echo esc_attr( $value['id'] ); ?>"
 									type="checkbox"
diff --git a/plugins/woocommerce/includes/class-wc-order-factory.php b/plugins/woocommerce/includes/class-wc-order-factory.php
index 543f2bf3915..973f6e5ec18 100644
--- a/plugins/woocommerce/includes/class-wc-order-factory.php
+++ b/plugins/woocommerce/includes/class-wc-order-factory.php
@@ -8,6 +8,9 @@
  * @package WooCommerce\Classes
  */
 
+use Automattic\WooCommerce\Caches\OrderCache;
+use Automattic\WooCommerce\Utilities\OrderUtil;
+
 defined( 'ABSPATH' ) || exit;
 
 use Automattic\WooCommerce\Utilities\OrderUtil;
@@ -30,13 +33,26 @@ class WC_Order_Factory {
 			return false;
 		}
 
+		$use_orders_cache = OrderUtil::orders_cache_usage_is_enabled();
+		if ( $use_orders_cache ) {
+			$order_cache = wc_get_container()->get( OrderCache::class );
+			$order       = $order_cache->get( $order_id );
+			if ( ! is_null( $order ) ) {
+				return $order;
+			}
+		}
+
 		$classname = self::get_class_name_for_order_id( $order_id );
 		if ( ! $classname ) {
 			return false;
 		}
 
 		try {
-			return new $classname( $order_id );
+			$order = new $classname( $order_id );
+			if ( $use_orders_cache && $order instanceof \WC_Abstract_Legacy_Order ) {
+				$order_cache->set( $order, $order_id );
+			}
+			return $order;
 		} catch ( Exception $e ) {
 			wc_caught_exception( $e, __FUNCTION__, array( $order_id ) );
 			return false;
@@ -56,6 +72,22 @@ class WC_Order_Factory {
 		$result    = array();
 		$order_ids = array_filter( array_map( array( __CLASS__, 'get_order_id' ), $order_ids ) );
 
+		$already_cached_orders = array();
+		$use_orders_cache      = OrderUtil::orders_cache_usage_is_enabled();
+		if ( $use_orders_cache ) {
+			$uncached_order_ids = array();
+			$order_cache        = wc_get_container()->get( OrderCache::class );
+			foreach ( $order_ids as $order_id ) {
+				$cached_order = $order_cache->get( absint( $order_id ) );
+				if ( is_null( $cached_order ) ) {
+					$uncached_order_ids[] = $order_id;
+				} else {
+					$already_cached_orders[] = $cached_order;
+				}
+			}
+			$order_ids = $uncached_order_ids;
+		}
+
 		// We separate order list by class, since their datastore might be different.
 		$order_list_by_class = array();
 		$order_id_classnames = self::get_class_names_for_order_ids( $order_ids );
@@ -99,9 +131,16 @@ class WC_Order_Factory {
 		}
 
 		// restore the sort order.
-		$result = array_replace( array_flip( $order_ids ), $result );
+		$result = array_values( array_replace( array_flip( $order_ids ), $result ) );
 
-		return array_values( $result );
+		if ( $use_orders_cache ) {
+			foreach ( $result as $order ) {
+				$order_cache->set( $order );
+			}
+			return array_merge( $already_cached_orders, $result );
+		} else {
+			return $result;
+		}
 	}
 
 	/**
diff --git a/plugins/woocommerce/src/Caches/OrderCache.php b/plugins/woocommerce/src/Caches/OrderCache.php
new file mode 100644
index 00000000000..f09adba3c62
--- /dev/null
+++ b/plugins/woocommerce/src/Caches/OrderCache.php
@@ -0,0 +1,44 @@
+<?php
+
+namespace Automattic\WooCommerce\Caches;
+
+use Automattic\WooCommerce\Caching\ObjectCache;
+
+/**
+ * A class to cache order objects.
+ */
+class OrderCache extends ObjectCache {
+
+	/**
+	 * Get the identifier for the type of the cached objects.
+	 *
+	 * @return string
+	 */
+	public function get_object_type(): string {
+		return 'order';
+	}
+
+	/**
+	 * Get the id of an object to be cached.
+	 *
+	 * @param array|object $object The object to be cached.
+	 * @return int|string|null The id of the object, or null if it can't be determined.
+	 */
+	protected function get_object_id( $object ) {
+		return $object->get_id();
+	}
+
+	/**
+	 * Validate an object before caching it.
+	 *
+	 * @param array|object $object The object to validate.
+	 * @return string[]|null An array of error messages, or null if the object is valid.
+	 */
+	protected function validate( $object ): ?array {
+		if ( ! $object instanceof \WC_Abstract_Legacy_Order ) {
+			return array( 'The supplied order is not an instance of WC_Order, ' . gettype( $object ) );
+		}
+
+		return null;
+	}
+}
diff --git a/plugins/woocommerce/src/Caches/OrderCacheController.php b/plugins/woocommerce/src/Caches/OrderCacheController.php
new file mode 100644
index 00000000000..6d89bb5309c
--- /dev/null
+++ b/plugins/woocommerce/src/Caches/OrderCacheController.php
@@ -0,0 +1,121 @@
+<?php
+
+namespace Automattic\WooCommerce\Caches;
+
+use Automattic\WooCommerce\Internal\Features\FeaturesController;
+use Automattic\WooCommerce\Internal\Traits\AccessiblePrivateMethods;
+
+/**
+ * A class to control the usage of the orders cache.
+ */
+class OrderCacheController {
+
+	use AccessiblePrivateMethods;
+
+	const FEATURE_NAME = 'orders_cache';
+
+	/**
+	 * The orders cache to use.
+	 *
+	 * @var OrderCache
+	 */
+	private $order_cache;
+
+	/**
+	 * The orders cache to use.
+	 *
+	 * @var FeaturesController
+	 */
+	private $features_controller;
+
+	/**
+	 * The backup value of the cache usage enable status, stored while the cache is temporarily disabled.
+	 *
+	 * @var null|bool
+	 */
+	private $orders_cache_usage_backup = null;
+
+	/**
+	 * Creates a new instance of the class.
+	 */
+	public function __construct() {
+		self::add_action( FeaturesController::FEATURE_ENABLED_CHANGED_ACTION, array( $this, 'handle_feature_enable_changed' ), 10, 2 );
+	}
+
+	/**
+	 * Class initialization, invoked by the DI container.
+	 *
+	 * @internal
+	 * @param OrderCache         $order_cache The order cache engine to use.
+	 * @param FeaturesController $features_controller The features controller to use.
+	 */
+	final public function init( OrderCache $order_cache, FeaturesController $features_controller ) {
+		$this->order_cache         = $order_cache;
+		$this->features_controller = $features_controller;
+	}
+
+	/**
+	 * Handler for the feature enable changed action, when the orders cache is enabled or disabled it flushes it.
+	 *
+	 * @param string $feature_id The id of the feature whose enable status changed.
+	 * @param bool   $enabled Whether the feature has been enabled or disabled.
+	 * @return void
+	 */
+	private function handle_feature_enable_changed( string $feature_id, bool $enabled ): void {
+		if ( self::FEATURE_NAME === $feature_id ) {
+			$this->order_cache->flush();
+		}
+	}
+
+	/**
+	 * Set the value of the order cache usage setting.
+	 *
+	 * @param bool $enable True if the order cache should be used, false if not.
+	 * @throws \Exception Attempt to enable the orders cache usage while it's temporarily disabled.
+	 */
+	public function set_orders_cache_usage( bool $enable ): void {
+		$this->features_controller->change_feature_enable( $enable );
+		$this->orders_cache_usage_backup = null;
+	}
+
+	/**
+	 * Get the value of the order cache usage setting.
+	 *
+	 * @return bool True if order cache usage setting is currently enabled, false if not.
+	 */
+	public function orders_cache_usage_is_enabled(): bool {
+		return ! $this->orders_cache_usage_is_temporarly_disabled() && $this->features_controller->feature_is_enabled( self::FEATURE_NAME );
+	}
+
+	/**
+	 * Temporarily disable the order cache if it's enabled.
+	 *
+	 * This is a purely in-memory operation: a variable is created with the value
+	 * of the current enable status for the feature, and this variable
+	 * is checked by orders_cache_usage_is_enabled. In the next request the
+	 * feature will be again enabled or not depending on how the feature is set.
+	 */
+	public function temporarily_disable_orders_cache_usage(): void {
+		if ( $this->orders_cache_usage_is_temporarly_disabled() ) {
+			return;
+		}
+
+		$this->orders_cache_usage_backup = $this->orders_cache_usage_is_enabled();
+	}
+
+	/**
+	 * Check if the order cache has been temporarily disabled.
+	 *
+	 * @return bool True if the order cache is currently temporarily disabled.
+	 */
+	public function orders_cache_usage_is_temporarly_disabled(): bool {
+		return null !== $this->orders_cache_usage_backup;
+	}
+
+	/**
+	 * Restore the order cache usage that had been temporarily disabled.
+	 */
+	public function maybe_restore_orders_cache_usage(): void {
+		$this->orders_cache_usage_backup = null;
+	}
+}
diff --git a/plugins/woocommerce/src/Caching/ObjectCache.php b/plugins/woocommerce/src/Caching/ObjectCache.php
index 2e86413069b..94b6de7e642 100644
--- a/plugins/woocommerce/src/Caching/ObjectCache.php
+++ b/plugins/woocommerce/src/Caching/ObjectCache.php
@@ -164,13 +164,13 @@ abstract class ObjectCache {
 	/**
 	 * Add an object to the cache, or update an already cached object.
 	 *
-	 * @param int|string|null $id Id of the object to be cached, if null, get_object_id will be used to get it.
 	 * @param object|array    $object The object to be cached.
+	 * @param int|string|null $id Id of the object to be cached, if null, get_object_id will be used to get it.
 	 * @param int             $expiration Expiration of the cached data in seconds from the current time, or DEFAULT_EXPIRATION to use the default value.
 	 * @return bool True on success, false on error.
 	 * @throws CacheException Invalid parameter, or null id was passed and get_object_id returns null too.
 	 */
-	public function set( $id = null, $object, int $expiration = self::DEFAULT_EXPIRATION ): bool {
+	public function set( $object, $id = null, int $expiration = self::DEFAULT_EXPIRATION ): bool {
 		if ( null === $object ) {
 			throw new CacheException( "Can't cache a null value", $this, $id );
 		}
@@ -185,20 +185,22 @@ abstract class ObjectCache {
 
 		$this->verify_expiration_value( $expiration );
 
-		if ( null === $id ) {
-			$id = $this->get_object_id( $object );
-			if ( null === $id ) {
-				throw new CacheException( "Null id supplied and the cache class doesn't implement get_object_id", $this );
+		$errors = $this->validate( $object );
+		if ( ! is_null( $errors ) ) {
+			try {
+				$id = $this->get_id_from_object_if_null( $object, $id );
+			} catch ( \Throwable $ex ) { // phpcs:ignore Generic.CodeAnalysis.EmptyStatement.DetectedCatch
+				// Nothing else to do, we won't be able to add any significant object id to the CacheException and that's it.
+			}
+
+			if ( count( $errors ) === 1 ) {
+				throw new CacheException( 'Object validation/serialization failed: ' . $errors[0], $this, $id, $errors );
+			} elseif ( ! empty( $errors ) ) {
+				throw new CacheException( 'Object validation/serialization failed', $this, $id, $errors );
 			}
 		}
 
-		$errors = $this->validate( $object );
-		if ( null !== $errors && 1 === count( $errors ) ) {
-			throw new CacheException( 'Object validation/serialization failed: ' . $errors[0], $this, $id, $errors );
-		} elseif ( ! empty( $errors ) ) {
-			throw new CacheException( 'Object validation/serialization failed', $this, $id, $errors );
-		}
-
+		$id   = $this->get_id_from_object_if_null( $object, $id );
 		$data = $this->serialize( $object );
 
 		/**
@@ -213,7 +215,49 @@ abstract class ObjectCache {
 		$data = apply_filters( "woocommerce_after_serializing_{$this->object_type}_for_caching", $data, $object, $id );
 
 		$this->last_cached_data = $data;
-		return $this->get_cache_engine()->cache_object( $this->get_cache_key_prefix() . $id, $data, self::DEFAULT_EXPIRATION === $expiration ? $this->default_expiration : $expiration );
+		return $this->get_cache_engine()->cache_object(
+			$this->get_cache_key_prefix() . $id,
+			$data,
+			self::DEFAULT_EXPIRATION === $expiration ? $this->default_expiration : $expiration
+		);
+	}
+
+	/**
+	 * Update an object in the cache, but only if an object is already cached with the same id.
+	 *
+	 * @param object|array    $object The new object that will replace the already cached one.
+	 * @param int|string|null $id Id of the object to be cached, if null, get_object_id will be used to get it.
+	 * @param int             $expiration Expiration of the cached data in seconds from the current time, or DEFAULT_EXPIRATION to use the default value.
+	 * @return bool True on success, false on error or if no object wiith the supplied id was cached.
+	 * @throws CacheException Invalid parameter, or null id was passed and get_object_id returns null too.
+	 */
+	public function update_if_cached( $object, $id = null, int $expiration = self::DEFAULT_EXPIRATION ): bool {
+		$id = $this->get_id_from_object_if_null( $object, $id );
+
+		if ( ! $this->is_cached( $id ) ) {
+			return false;
+		}
+
+		return $this->set( $object, $id, $expiration );
+	}
+
+	/**
+	 * Get the id from an object if the id itself is null.
+	 *
+	 * @param object|array    $object The object to get the id from.
+	 * @param int|string|null $id An object id or null.
+	 * @return int|string|null Passed $id if it wasn't null, otherwise id obtained from $object using get_object_id.
+	 * @throws CacheException Passed $id is null and get_object_id returned null too.
+	 */
+	private function get_id_from_object_if_null( $object, $id ) {
+		if ( null === $id ) {
+			$id = $this->get_object_id( $object );
+			if ( null === $id ) {
+				throw new CacheException( "Null id supplied and the cache class doesn't implement get_object_id", $this );
+			}
+		}
+
+		return $id;
 	}
 
 	/**
@@ -261,7 +305,7 @@ abstract class ObjectCache {
 				return null;
 			}
 
-			$this->set( $id, $object, $expiration );
+			$this->set( $object, $id, $expiration );
 			$data = $this->last_cached_data;
 		}
 
diff --git a/plugins/woocommerce/src/Internal/DataStores/Orders/CustomOrdersTableController.php b/plugins/woocommerce/src/Internal/DataStores/Orders/CustomOrdersTableController.php
index 3ceeb399229..29e8cea6f1e 100644
--- a/plugins/woocommerce/src/Internal/DataStores/Orders/CustomOrdersTableController.php
+++ b/plugins/woocommerce/src/Internal/DataStores/Orders/CustomOrdersTableController.php
@@ -5,9 +5,12 @@
 
 namespace Automattic\WooCommerce\Internal\DataStores\Orders;
 
+use Automattic\WooCommerce\Caches\OrderCache;
+use Automattic\WooCommerce\Caches\OrderCacheController;
 use Automattic\WooCommerce\Internal\BatchProcessing\BatchProcessingController;
 use Automattic\WooCommerce\Internal\Features\FeaturesController;
 use Automattic\WooCommerce\Internal\Traits\AccessiblePrivateMethods;
+use Automattic\WooCommerce\Utilities\OrderUtil;
 
 defined( 'ABSPATH' ) || exit;
 
@@ -81,6 +84,20 @@ class CustomOrdersTableController {
 	 */
 	private $features_controller;
 
+	/**
+	 * The orders cache object to use.
+	 *
+	 * @var OrderCache
+	 */
+	private $order_cache;
+
+	/**
+	 * The orders cache controller object to use.
+	 *
+	 * @var OrderCacheController
+	 */
+	private $order_cache_controller;
+
 	/**
 	 * Class constructor.
 	 */
@@ -114,18 +131,24 @@ class CustomOrdersTableController {
 	 * @param OrdersTableRefundDataStore $refund_data_store The refund data store to use.
 	 * @param BatchProcessingController  $batch_processing_controller The batch processing controller to use.
 	 * @param FeaturesController         $features_controller The features controller instance to use.
+	 * @param OrderCache                 $order_cache The order cache engine to use.
+	 * @param OrderCacheController       $order_cache_controller The order cache controller to use.
 	 */
 	final public function init(
 		OrdersTableDataStore $data_store,
 		DataSynchronizer $data_synchronizer,
 		OrdersTableRefundDataStore $refund_data_store,
 		BatchProcessingController $batch_processing_controller,
-		FeaturesController $features_controller ) {
+		FeaturesController $features_controller,
+		OrderCache $order_cache,
+		OrderCacheController $order_cache_controller ) {
 		$this->data_store                  = $data_store;
 		$this->data_synchronizer           = $data_synchronizer;
 		$this->batch_processing_controller = $batch_processing_controller;
 		$this->refund_data_store           = $refund_data_store;
 		$this->features_controller         = $features_controller;
+		$this->order_cache                 = $order_cache;
+		$this->order_cache_controller      = $order_cache_controller;
 	}
 
 	/**
@@ -466,8 +489,14 @@ class CustomOrdersTableController {
 			return $value;
 		}
 
+		if ( self::CUSTOM_ORDERS_TABLE_USAGE_ENABLED_OPTION !== $option || $value === $old_value || false === $old_value ) {
+			return $value;
+		}
+
+		$this->order_cache->flush();
+
 		/**
-		 * Commenting out for better testability.
+		 * TODO: Re-enable the following code once the COT to posts table sync is implemented (it's currently commented out to ease testing).
 		$sync_is_pending = 0 !== $this->data_synchronizer->get_current_orders_pending_sync_count();
 		if ( $sync_is_pending ) {
 			throw new \Exception( "The authoritative table for orders storage can't be changed while there are orders out of sync" );
@@ -575,4 +604,15 @@ class CustomOrdersTableController {
 			)
 		);
 	}
+
+	/**
+	 * Handle the order deleted/trashed hooks.
+	 *
+	 * @param int $order_id The id of the order deleted or trashed.
+	 */
+	private function after_order_deleted_or_trashed( int $order_id ): void {
+		if ( $this->features_controller->feature_is_enabled( OrderCacheController::FEATURE_NAME ) ) {
+			$this->order_cache->remove( $order_id );
+		}
+	}
 }
diff --git a/plugins/woocommerce/src/Internal/DataStores/Orders/DataSynchronizer.php b/plugins/woocommerce/src/Internal/DataStores/Orders/DataSynchronizer.php
index efb50a8940c..5df64183cae 100644
--- a/plugins/woocommerce/src/Internal/DataStores/Orders/DataSynchronizer.php
+++ b/plugins/woocommerce/src/Internal/DataStores/Orders/DataSynchronizer.php
@@ -5,6 +5,8 @@
 
 namespace Automattic\WooCommerce\Internal\DataStores\Orders;
 
+use Automattic\WooCommerce\Caches\OrderCache;
+use Automattic\WooCommerce\Caches\OrderCacheController;
 use Automattic\WooCommerce\Database\Migrations\CustomOrderTable\PostsToOrdersMigrationController;
 use Automattic\WooCommerce\Internal\BatchProcessing\BatchProcessorInterface;
 use Automattic\WooCommerce\Internal\Features\FeaturesController;
@@ -111,6 +113,7 @@ class DataSynchronizer implements BatchProcessorInterface {
 	 * Delete the custom orders database tables.
 	 */
 	public function delete_database_tables() {
+		$this->cache->flush();
 		$table_names = $this->data_store->get_all_table_names();
 
 		foreach ( $table_names as $table_name ) {
@@ -329,6 +332,8 @@ WHERE
 	 * @param array $batch Batch details.
 	 */
 	public function process_batch( array $batch ) : void {
+		$this->cache_controller->temporarily_disable_orders_cache_usage();
+
 		if ( $this->custom_orders_table_is_authoritative() ) {
 			foreach ( $batch as $id ) {
 				$order = wc_get_order( $id );
@@ -344,6 +349,7 @@ WHERE
 		}
 		if ( 0 === $this->get_total_pending_count() ) {
 			$this->cleanup_synchronization_state();
+			$this->cache_controller->maybe_restore_orders_cache_usage();
 		}
 	}
 
diff --git a/plugins/woocommerce/src/Internal/DependencyManagement/ServiceProviders/COTMigrationServiceProvider.php b/plugins/woocommerce/src/Internal/DependencyManagement/ServiceProviders/COTMigrationServiceProvider.php
index f1e95332559..92c338b296d 100644
--- a/plugins/woocommerce/src/Internal/DependencyManagement/ServiceProviders/COTMigrationServiceProvider.php
+++ b/plugins/woocommerce/src/Internal/DependencyManagement/ServiceProviders/COTMigrationServiceProvider.php
@@ -7,7 +7,6 @@ namespace Automattic\WooCommerce\Internal\DependencyManagement\ServiceProviders;
 
 use Automattic\WooCommerce\DataBase\Migrations\CustomOrderTable\CLIRunner;
 use Automattic\WooCommerce\Database\Migrations\CustomOrderTable\PostsToOrdersMigrationController;
-use Automattic\WooCommerce\Internal\DataStores\Orders\DataSynchronizer;
 use Automattic\WooCommerce\Internal\DependencyManagement\AbstractServiceProvider;
 
 /**
@@ -25,7 +24,6 @@ class COTMigrationServiceProvider extends AbstractServiceProvider {
 	protected $provides = array(
 		PostsToOrdersMigrationController::class,
 		CLIRunner::class,
-		DataSynchronizer::class,
 	);
 
 	/**
@@ -37,5 +35,6 @@ class COTMigrationServiceProvider extends AbstractServiceProvider {
 	 */
 	public function register() {
 		$this->share( PostsToOrdersMigrationController::class );
+		$this->share( CLIRunner::class );
 	}
 }
diff --git a/plugins/woocommerce/src/Internal/DependencyManagement/ServiceProviders/OrdersDataStoreServiceProvider.php b/plugins/woocommerce/src/Internal/DependencyManagement/ServiceProviders/OrdersDataStoreServiceProvider.php
index 4e4b0b18c5e..e1e207fe82b 100644
--- a/plugins/woocommerce/src/Internal/DependencyManagement/ServiceProviders/OrdersDataStoreServiceProvider.php
+++ b/plugins/woocommerce/src/Internal/DependencyManagement/ServiceProviders/OrdersDataStoreServiceProvider.php
@@ -6,6 +6,9 @@
 namespace Automattic\WooCommerce\Internal\DependencyManagement\ServiceProviders;
 
 use Automattic\Jetpack\Constants;
+use Automattic\WooCommerce\Caches\OrderCache;
+use Automattic\WooCommerce\Caches\OrderCacheController;
+use Automattic\WooCommerce\Caching\TransientsEngine;
 use Automattic\WooCommerce\DataBase\Migrations\CustomOrderTable\CLIRunner;
 use Automattic\WooCommerce\Database\Migrations\CustomOrderTable\PostsToOrdersMigrationController;
 use Automattic\WooCommerce\Internal\BatchProcessing\BatchProcessingController;
@@ -36,6 +39,8 @@ class OrdersDataStoreServiceProvider extends AbstractServiceProvider {
 		CLIRunner::class,
 		OrdersTableDataStoreMeta::class,
 		OrdersTableRefundDataStore::class,
+		OrderCache::class,
+		OrderCacheController::class,
 	);
 
 	/**
@@ -54,6 +59,8 @@ class OrdersDataStoreServiceProvider extends AbstractServiceProvider {
 				OrdersTableRefundDataStore::class,
 				BatchProcessingController::class,
 				FeaturesController::class,
+				OrderCache::class,
+				OrderCacheController::class,
 			)
 		);
 
diff --git a/plugins/woocommerce/src/Internal/Features/FeaturesController.php b/plugins/woocommerce/src/Internal/Features/FeaturesController.php
index 9a10192ad11..c5096334c5d 100644
--- a/plugins/woocommerce/src/Internal/Features/FeaturesController.php
+++ b/plugins/woocommerce/src/Internal/Features/FeaturesController.php
@@ -111,6 +111,11 @@ class FeaturesController {
 				'description'     => __( 'Enable the high performance order storage feature.', 'woocommerce' ),
 				'is_experimental' => true,
 			),
+			OrderCacheController::FEATURE_NAME => array(
+				'name'            => __( 'Orders cache', 'woocommerce' ),
+				'description'     => __( 'Enable the usage of a cache for shop orders', 'woocommerce' ),
+				'is_experimental' => true,
+			),
 		);
 
 		$this->legacy_feature_ids = array( 'analytics', 'new_navigation', 'new_product_management' );
diff --git a/plugins/woocommerce/src/Utilities/OrderUtil.php b/plugins/woocommerce/src/Utilities/OrderUtil.php
index e8bee281a72..1a609058a01 100644
--- a/plugins/woocommerce/src/Utilities/OrderUtil.php
+++ b/plugins/woocommerce/src/Utilities/OrderUtil.php
@@ -5,8 +5,10 @@
 
 namespace Automattic\WooCommerce\Utilities;
 
+use Automattic\WooCommerce\Caches\OrderCacheController;
 use Automattic\WooCommerce\Internal\Admin\Orders\PageController;
 use Automattic\WooCommerce\Internal\DataStores\Orders\CustomOrdersTableController;
+use Automattic\WooCommerce\Internal\Features\FeaturesController;
 use Automattic\WooCommerce\Internal\Utilities\COTMigrationUtil;
 use WC_Order;
 use WP_Post;
@@ -35,6 +37,15 @@ final class OrderUtil {
 		return wc_get_container()->get( CustomOrdersTableController::class )->custom_orders_table_usage_is_enabled();
 	}
 
+	/**
+	 * Helper function to get whether the orders cache should be used or not.
+	 *
+	 * @return bool True if the orders cache should be used, false otherwise.
+	 */
+	public static function orders_cache_usage_is_enabled() : bool {
+		return wc_get_container()->get( OrderCacheController::class )->orders_cache_usage_is_enabled();
+	}
+
 	/**
 	 * Checks if posts and order custom table sync is enabled and there are no pending orders.
 	 *
diff --git a/plugins/woocommerce/tests/php/includes/rest-api/Controllers/Version3/class-wc-rest-orders-controller-tests.php b/plugins/woocommerce/tests/php/includes/rest-api/Controllers/Version3/class-wc-rest-orders-controller-tests.php
index 670a35b3f75..95501cbf8ea 100644
--- a/plugins/woocommerce/tests/php/includes/rest-api/Controllers/Version3/class-wc-rest-orders-controller-tests.php
+++ b/plugins/woocommerce/tests/php/includes/rest-api/Controllers/Version3/class-wc-rest-orders-controller-tests.php
@@ -230,8 +230,9 @@ class WC_REST_Orders_Controller_Tests extends WC_REST_Unit_Test_Case {
 		$order = new \WC_Order();
 		$order->set_status( 'completed' );
 		$order->save();
+		$order_id = $order->get_id();
 
-		$request  = new \WP_REST_Request( 'DELETE', '/wc/v3/orders/' . $order->get_id() );
+		$request  = new \WP_REST_Request( 'DELETE', '/wc/v3/orders/' . $order_id );
 		$response = $this->server->dispatch( $request );
 
 		$this->assertEquals( 200, $response->get_status() );
@@ -239,13 +240,13 @@ class WC_REST_Orders_Controller_Tests extends WC_REST_Unit_Test_Case {
 		// Check that the response includes order data from the order (before deletion).
 		$data = $response->get_data();
 		$this->assertArrayHasKey( 'id', $data );
-		$this->assertEquals( $data['id'], $order->get_id() );
+		$this->assertEquals( $data['id'], $order_id );
 		$this->assertEquals( 'completed', $data['status'] );
 
 		wp_cache_flush();
 
 		// Check the order was actually deleted.
-		$order = wc_get_order( $order->get_id() );
+		$order = wc_get_order( $order_id );
 		$this->assertEquals( 'trash', $order->get_status( 'edit' ) );
 	}
 
diff --git a/plugins/woocommerce/tests/php/src/Caching/ObjectCacheTest.php b/plugins/woocommerce/tests/php/src/Caching/ObjectCacheTest.php
index be63d540f93..27979185713 100644
--- a/plugins/woocommerce/tests/php/src/Caching/ObjectCacheTest.php
+++ b/plugins/woocommerce/tests/php/src/Caching/ObjectCacheTest.php
@@ -94,7 +94,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 		$this->expectException( CacheException::class );
 		$this->expectExceptionMessage( "Can't cache a null value" );
 
-		$this->sut->set( 'the_id', null );
+		$this->sut->set( null );
 	}
 
 	/**
@@ -104,7 +104,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 		$this->expectException( CacheException::class );
 		$this->expectExceptionMessage( "Can't cache a non-object, non-array value" );
 
-		$this->sut->set( 'the_id', 1234 );
+		$this->sut->set( 1234 );
 	}
 
 	/**
@@ -114,7 +114,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 		$this->expectException( CacheException::class );
 		$this->expectExceptionMessage( "Object id must be an int, a string, or null for 'set'" );
 
-		$this->sut->set( array( 1, 2 ), array( 'foo' ) );
+		$this->sut->set( array( 'foo' ), array( 1, 2 ) );
 	}
 
 	/**
@@ -130,7 +130,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 		$this->expectException( CacheException::class );
 		$this->expectExceptionMessage( 'Invalid expiration value, must be ObjectCache::DEFAULT_EXPIRATION or a value between 1 and ObjectCache::MAX_EXPIRATION' );
 
-		$this->sut->set( 'the_id', array( 'foo' ), $expiration );
+		$this->sut->set( array( 'foo' ), 'the_id', $expiration );
 	}
 
 	/**
@@ -139,7 +139,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 	public function try_set_when_cache_engine_fails() {
 		$this->cache_engine->caching_succeeds = false;
 
-		$result = $this->sut->set( 'the_id', array( 'foo' ) );
+		$result = $this->sut->set( array( 'foo' ), 'the_id' );
 		$this->assertFalse( $result );
 	}
 
@@ -148,7 +148,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 	 */
 	public function test_set_new_object_with_id_caches_with_expected_key() {
 		$object = array( 'foo' );
-		$result = $this->sut->set( 'the_id', $object );
+		$result = $this->sut->set( $object, 'the_id' );
 
 		$this->assertTrue( $result );
 
@@ -165,9 +165,9 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 	 */
 	public function test_setting_two_objects_result_in_same_prefix() {
 		$object_1 = array( 'foo' );
-		$this->sut->set( 'the_id_1', $object_1 );
+		$this->sut->set( $object_1, 'the_id_1' );
 		$object_2 = array( 1, 2, 3, 4 );
-		$this->sut->set( 9999, $object_2 );
+		$this->sut->set( $object_2, 9999 );
 
 		$prefix = 'woocommerce_object_cache|the_type|random_1|';
 
@@ -183,7 +183,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 	 * @testdox 'set' uses the default expiration value if no explicit value is passed.
 	 */
 	public function test_set_with_default_expiration() {
-		$this->sut->set( 'the_id', array( 'foo' ) );
+		$this->sut->set( array( 'foo' ), 'the_id' );
 		$this->assertEquals( $this->sut->get_default_expiration_value(), $this->cache_engine->last_expiration );
 	}
 
@@ -191,7 +191,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 	 * @testdox 'set' uses the explicitly passed expiration value.
 	 */
 	public function test_set_with_explicit_expiration() {
-		$this->sut->set( 'the_id', array( 'foo' ), 1234 );
+		$this->sut->set( array( 'foo' ), 'the_id', 1234 );
 		$this->assertEquals( 1234, $this->cache_engine->last_expiration );
 	}
 
@@ -202,7 +202,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 		$this->expectException( CacheException::class );
 		$this->expectExceptionMessage( "Null id supplied and the cache class doesn't implement get_object_id" );
 
-		$this->sut->set( null, array( 'foo' ) );
+		$this->sut->set( array( 'foo' ) );
 	}
 
 	/**
@@ -227,11 +227,88 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 
 		// phpcs:enable Squiz.Commenting
 
-		$sut->set( null, array( 'id' => 1234 ) );
+		$sut->set( array( 'id' => 1234 ) );
 
 		$this->assertEquals( 'woocommerce_object_cache|the_type|random|1235', array_keys( $this->cache_engine->cache )[0] );
 	}
 
+	/**
+	 * @testdox 'update_if_cached' does nothing if no object is cached with the passed (or obtained) id.
+	 *
+	 * @testWith [1234]
+	 *           [null]
+	 *
+	 * @param ?int $id Id to pass to update_if_cached.
+	 */
+	public function test_update_if_cached_does_nothing_for_not_cached_id( ?int $id ) {
+		// phpcs:disable Squiz.Commenting
+
+		$sut = new class() extends ObjectCache {
+			public function get_object_type(): string {
+				return 'the_type';
+			}
+
+			protected function get_object_id( $object ) {
+				return $object['id'];
+			}
+		};
+
+		// phpcs:enable Squiz.Commenting
+
+		$result = $sut->update_if_cached( array( 'id' => 1234 ), $id );
+		$this->assertFalse( $result );
+		$this->assertEmpty( $this->cache_engine->cache );
+	}
+
+	/**
+	 * @testdox 'update_if_cached' updates an already cached object the same way as 'set'.
+	 *
+	 * @testWith [1234]
+	 *           [null]
+	 *
+	 * @param ?int $id Id to pass to update_if_cached.
+	 */
+	public function test_update_if_cached_updates_already_cached_object( ?int $id ) {
+		// phpcs:disable Squiz.Commenting
+
+		$sut = new class() extends ObjectCache {
+			public function get_object_type(): string {
+				return 'the_type';
+			}
+
+			protected function get_object_id( $object ) {
+				return $object['id'];
+			}
+
+			protected function get_random_string(): string {
+				return 'random';
+			}
+		};
+
+		// phpcs:enable Squiz.Commenting
+
+		$sut->set( array( 'id' => 1234 ), $id );
+		$this->assertEquals( 'woocommerce_object_cache|the_type|random|1234', array_keys( $this->cache_engine->cache )[0] );
+
+		$new_value = array(
+			'id'  => 1234,
+			'foo' => 'bar',
+		);
+		$result    = $sut->update_if_cached( $new_value, $id );
+		$this->assertTrue( $result );
+		$this->assertEquals( $this->cache_engine->cache['woocommerce_object_cache|the_type|random|1234'], array( 'data' => $new_value ) );
+	}
+
+	/**
+	 * @testdox 'update_if_cached' throws an exception if no object id is passed and the class doesn't implement 'get_object_id'.
+	 */
+	public function test_update_if_cached_null_id_without_id_retrieval_implementation() {
+		$this->expectException( CacheException::class );
+		$this->expectExceptionMessage( "Null id supplied and the cache class doesn't implement get_object_id" );
+
+		$this->sut->update_if_cached( array( 'foo' ) );
+	}
+
 	/**
 	 * @testdox 'set' caches the value returned by 'serialize'.
 	 */
@@ -252,7 +329,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 
 		// phpcs:enable Squiz.Commenting
 
-		$sut->set( 1234, $object );
+		$sut->set( $object, 1234 );
 
 		$cached   = array_values( $this->cache_engine->cache )[0];
 		$expected = array( 'the_data' => $object );
@@ -269,7 +346,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 	 */
 	public function test_set_with_custom_serialization_that_returns_errors( int $errors_count ) {
 		$exception = null;
-		$errors    = 1 === $errors_count ? array( 'Foo failed' ) : array( 'Foo failed', 'Bar failed' );
+		$errors    = $errors_count === 1 ? array( 'Foo failed' ) : array( 'Foo failed', 'Bar failed' );
 		$object    = array( 'foo' );
 
 		// phpcs:disable Squiz.Commenting
@@ -293,13 +370,13 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 		// phpcs:enable Squiz.Commenting
 
 		try {
-			$sut->set( 1234, $object );
+			$sut->set( $object, 1234 );
 		} catch ( CacheException $thrown ) {
 			$exception = $thrown;
 		}
 
 		$expected_message = 'Object validation/serialization failed';
-		if ( 1 === $errors_count ) {
+		if ( $errors_count === 1 ) {
 			$expected_message .= ': Foo failed';
 		}
 		$this->assertEquals( $expected_message, $exception->getMessage() );
@@ -343,7 +420,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 	 */
 	public function test_try_getting_previously_cached_object() {
 		$object = array( 'foo' );
-		$this->sut->set( 'the_id', $object );
+		$this->sut->set( $object, 'the_id' );
 
 		$result = $this->sut->get( 'the_id' );
 		$this->assertEquals( $object, $result );
@@ -465,7 +542,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 
 		// phpcs:enable Squiz.Commenting
 
-		$sut->set( 'the_id', array( 1, 2 ) );
+		$sut->set( array( 1, 2 ), 'the_id' );
 
 		$result   = $sut->get( 'the_id' );
 		$expected = array( 1, 2, 3 );
@@ -476,8 +553,8 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 	 * @testdox 'remove' removes a cached object and returns true, or returns false if there's no cached object under the passed id.
 	 */
 	public function test_remove() {
-		$this->sut->set( 'the_id_1', array( 'foo' ) );
-		$this->sut->set( 'the_id_2', array( 'bar' ) );
+		$this->sut->set( array( 'foo' ), 'the_id_1' );
+		$this->sut->set( array( 'bar' ), 'the_id_2' );
 
 		$result_1 = $this->sut->remove( 'the_id_1' );
 		$result_2 = $this->sut->remove( 'the_id_X' );
@@ -493,12 +570,12 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 	 * @testdox 'flush' deletes the stored cache key prefix, effectively rendering the cached objects inaccessible.
 	 */
 	public function test_flush() {
-		$this->sut->set( 'the_id', array( 'foo' ) );
+		$this->sut->set( array( 'foo' ), 'the_id' );
 
 		$this->sut->flush();
 		$this->assertFalse( get_option( 'wp_object_cache_key_prefix_the_type' ) );
 
-		$this->sut->set( 'the_id_2', array( 'bar' ) );
+		$this->sut->set( array( 'bar' ), 'the_id_2' );
 
 		$expected_new_prefix = 'woocommerce_object_cache|the_type|random_2|';
 		$this->assertEquals( $expected_new_prefix, get_option( 'wp_object_cache_key_prefix_the_type' ) );
@@ -534,7 +611,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 		// phpcs:enable Squiz.Commenting
 
 		$object = array( 'foo' );
-		$sut->set( 'the_id', $object );
+		$sut->set( $object, 'the_id' );
 
 		$expected_cached = array( 'data' => $object );
 		$this->assertEquals( $expected_cached, array_values( $engine->cache )[0] );
@@ -560,7 +637,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 		);
 
 		$object = array( 'foo' );
-		$this->sut->set( 'the_id', $object );
+		$this->sut->set( $object, 'the_id' );
 
 		$expected_cached = array( 'data' => $object );
 		$this->assertEquals( $expected_cached, array_values( $engine->cache )[0] );
@@ -590,7 +667,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 		);
 
 		$object = array( 'fizz' );
-		$this->sut->set( 'the_id', $object );
+		$this->sut->set( $object, 'the_id' );
 
 		$expected_cached = array(
 			'data' => $object,
@@ -626,7 +703,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 			3
 		);
 
-		$this->sut->set( 'the_id', $original_object );
+		$this->sut->set( $original_object, 'the_id' );
 		$retrieved_object = $this->sut->get( 'the_id' );
 
 		$this->assertEquals( $replacement_object, $retrieved_object );
@@ -658,7 +735,7 @@ class ObjectCacheTest extends \WC_Unit_Test_Case {
 			2
 		);
 
-		$this->sut->set( 'the_id', array( 'foo' ) );
+		$this->sut->set( array( 'foo' ), 'the_id' );
 		$this->sut->remove( $operation_succeeds ? 'the_id' : 'INVALID_ID' );
 
 		$this->assertEquals( $operation_succeeds ? 'the_id' : 'INVALID_ID', $id_passed_to_action );