diff --git a/ghost/core/core/server/services/collections/BookshelfCollectionsRepository.js b/ghost/core/core/server/services/collections/BookshelfCollectionsRepository.js
index f62ad52d21..3a05bfccf1 100644
--- a/ghost/core/core/server/services/collections/BookshelfCollectionsRepository.js
+++ b/ghost/core/core/server/services/collections/BookshelfCollectionsRepository.js
@@ -1,6 +1,7 @@
 const logger = require('@tryghost/logging');
 const Collection = require('@tryghost/collections').Collection;
 const sentry = require('../../../shared/sentry');
+const {default: ObjectID} = require('bson-objectid');
 /**
  * @typedef {import('@tryghost/collections/src/CollectionRepository')} CollectionRepository
  */
@@ -10,8 +11,10 @@ const sentry = require('../../../shared/sentry');
  */
 module.exports = class BookshelfCollectionsRepository {
     #model;
-    constructor(model) {
+    #relationModel;
+    constructor(model, relationModel) {
         this.#model = model;
+        this.#relationModel = relationModel;
     }
 
     async createTransaction(cb) {
@@ -101,10 +104,21 @@ module.exports = class BookshelfCollectionsRepository {
      * @returns {Promise<void>}
      */
     async save(collection, options = {}) {
+        if (!options.transaction) {
+            return this.createTransaction((transaction) => {
+                return this.save(collection, {
+                    ...options,
+                    transaction
+                });
+            });
+        }
+
         if (collection.deleted) {
-            await this.#model.destroy({id: collection.id});
+            await this.#relationModel.query().delete().where('collection_id', collection.id).transacting(options.transaction);
+            await this.#model.query().delete().where('id', collection.id).transacting(options.transaction);
             return;
         }
+
         const data = {
             id: collection.id,
             slug: collection.slug,
@@ -113,7 +127,6 @@ module.exports = class BookshelfCollectionsRepository {
             filter: collection.filter,
             type: collection.type,
             feature_image: collection.featureImage || null,
-            posts: collection.posts.map(postId => ({id: postId})),
             created_at: collection.createdAt,
             updated_at: collection.updatedAt
         };
@@ -122,7 +135,8 @@ module.exports = class BookshelfCollectionsRepository {
             {id: data.id},
             {
                 require: false,
-                transacting: options.transaction
+                transacting: options.transaction,
+                withRelated: ['collectionPosts']
             }
         );
 
@@ -130,11 +144,59 @@ module.exports = class BookshelfCollectionsRepository {
             await this.#model.add(data, {
                 transacting: options.transaction
             });
+            const collectionPostsRelations = collection.posts.map((postId, index) => {
+                return {
+                    id: (new ObjectID).toHexString(),
+                    sort_order: collection.type === 'manual' ? index : 0,
+                    collection_id: collection.id,
+                    post_id: postId
+                };
+            });
+            if (collectionPostsRelations.length > 0) {
+                await this.#relationModel.query().insert(collectionPostsRelations).transacting(options.transaction);
+            }
         } else {
-            return this.#model.edit(data, {
+            await this.#model.edit(data, {
                 id: data.id,
                 transacting: options.transaction
             });
+
+            const collectionPostsRelations = collection.posts.map((postId, index) => {
+                return {
+                    id: (new ObjectID).toHexString(),
+                    sort_order: collection.type === 'manual' ? index : 0,
+                    collection_id: collection.id,
+                    post_id: postId
+                };
+            });
+
+            const collectionPostRelationsToDeleteIds = [];
+
+            if (collection.type === 'manual') {
+                await this.#relationModel.query().delete().where('collection_id', collection.id).transacting(options.transaction);
+            } else {
+                const existingRelations = existing.toJSON().collectionPosts;
+
+                for (const existingRelation of existingRelations) {
+                    const found = collectionPostsRelations.find((thing) => {
+                        return thing.post_id === existingRelation.post_id;
+                    });
+                    if (found) {
+                        found.id = null;
+                    } else {
+                        collectionPostRelationsToDeleteIds.push(existingRelation.id);
+                    }
+                }
+            }
+
+            const missingCollectionPostsRelations = collectionPostsRelations.filter(thing => thing.id !== null);
+
+            if (missingCollectionPostsRelations.length > 0) {
+                await this.#relationModel.query().insert(missingCollectionPostsRelations).transacting(options.transaction);
+            }
+            if (collectionPostRelationsToDeleteIds.length > 0) {
+                await this.#relationModel.query().delete().whereIn('id', collectionPostRelationsToDeleteIds).transacting(options.transaction);
+            }
         }
     }
 };
diff --git a/ghost/core/core/server/services/collections/service.js b/ghost/core/core/server/services/collections/service.js
index bcbe488b59..3bdc9faf72 100644
--- a/ghost/core/core/server/services/collections/service.js
+++ b/ghost/core/core/server/services/collections/service.js
@@ -12,7 +12,7 @@ class CollectionsServiceWrapper {
         const DomainEvents = require('@tryghost/domain-events');
         const postsRepository = require('./PostsRepository').getInstance();
         const models = require('../../models');
-        const collectionsRepositoryInMemory = new BookshelfCollectionsRepository(models.Collection);
+        const collectionsRepositoryInMemory = new BookshelfCollectionsRepository(models.Collection, models.CollectionPost);
 
         const collectionsService = new CollectionsService({
             collectionsRepository: collectionsRepositoryInMemory,
diff --git a/ghost/core/test/e2e-api/admin/posts-bulk.test.js b/ghost/core/test/e2e-api/admin/posts-bulk.test.js
index 1318d72884..3714dc007e 100644
--- a/ghost/core/test/e2e-api/admin/posts-bulk.test.js
+++ b/ghost/core/test/e2e-api/admin/posts-bulk.test.js
@@ -30,8 +30,8 @@ describe('Posts Bulk API', function () {
 
             assert(amount > 0, 'Expect at least one post to be affected for this test to work');
 
-            let featuredCollection = await models.Collection.findPage({filter: 'slug:featured', limit: 1, withRelated: ['posts']});
-            let featuredCollectionPostsAmount = featuredCollection.data[0].toJSON().posts.length;
+            let featuredCollection = await models.Collection.findPage({filter: 'slug:featured', limit: 1, withRelated: ['collectionPosts']});
+            let featuredCollectionPostsAmount = featuredCollection.data[0].toJSON().collectionPosts.length;
             assert(featuredCollectionPostsAmount > 0, 'Expect to have multiple featured collection posts');
 
             const response = await agent
@@ -52,8 +52,8 @@ describe('Posts Bulk API', function () {
             const posts = await models.Post.findAll({filter, status: 'all'});
             assert.equal(posts.length, amount, `Expect all matching posts (${amount}) to be changed`);
 
-            featuredCollection = await models.Collection.findPage({filter: 'slug:featured', limit: 1, withRelated: ['posts']});
-            featuredCollectionPostsAmount = featuredCollection.data[0].toJSON().posts.length;
+            featuredCollection = await models.Collection.findPage({filter: 'slug:featured', limit: 1, withRelated: ['collectionPosts']});
+            featuredCollectionPostsAmount = featuredCollection.data[0].toJSON().collectionPosts.length;
             assert.equal(featuredCollectionPostsAmount, amount, 'Expect to have same amount featured collection posts as changed');
 
             for (const post of posts) {
@@ -70,8 +70,8 @@ describe('Posts Bulk API', function () {
 
             assert(amount > 0, 'Expect at least one post to be affected for this test to work');
 
-            let featuredCollection = await models.Collection.findPage({filter: 'slug:featured', limit: 1, withRelated: ['posts']});
-            let featuredCollectionPostsAmount = featuredCollection.data[0].toJSON().posts.length;
+            let featuredCollection = await models.Collection.findPage({filter: 'slug:featured', limit: 1, withRelated: ['collectionPosts']});
+            let featuredCollectionPostsAmount = featuredCollection.data[0].toJSON().collectionPosts.length;
             assert(featuredCollectionPostsAmount > 0, 'Expect to have multiple featured collection posts');
 
             const response = await agent
@@ -92,8 +92,8 @@ describe('Posts Bulk API', function () {
             const posts = await models.Post.findAll({filter, status: 'all'});
             assert.equal(posts.length, amount, `Expect all matching posts (${amount}) to be changed`);
 
-            featuredCollection = await models.Collection.findPage({filter: 'slug:featured', limit: 1, withRelated: ['posts']});
-            featuredCollectionPostsAmount = featuredCollection.data[0].toJSON().posts.length;
+            featuredCollection = await models.Collection.findPage({filter: 'slug:featured', limit: 1, withRelated: ['collectionPosts']});
+            featuredCollectionPostsAmount = featuredCollection.data[0].toJSON().collectionPosts.length;
             assert.equal(featuredCollectionPostsAmount, 0, 'Expect to have no featured collection posts');
 
             for (const post of posts) {
@@ -354,8 +354,8 @@ describe('Posts Bulk API', function () {
             const posts = await models.Post.findPage({filter, status: 'all'});
             assert.equal(posts.meta.pagination.total, 0, `Expect all matching posts (${amount}) to be deleted`);
 
-            let latestCollection = await models.Collection.findPage({filter: 'slug:latest', limit: 1, withRelated: ['posts']});
-            latestCollection = latestCollection.data[0].toJSON().posts.length;
+            let latestCollection = await models.Collection.findPage({filter: 'slug:latest', limit: 1, withRelated: ['collectionPosts']});
+            latestCollection = latestCollection.data[0].toJSON().collectionPosts.length;
             assert.equal(latestCollection, 0, 'Expect to have no collection posts');
         });
     });