diff --git a/backend/app/models/post_version.rb b/backend/app/models/post_version.rb
index a11ee89..c933813 100644
--- a/backend/app/models/post_version.rb
+++ b/backend/app/models/post_version.rb
@@ -11,9 +11,12 @@ class PostVersion < ApplicationRecord
   belongs_to :parent, class_name: 'Post', optional: true
   belongs_to :created_by_user, class_name: 'User', optional: true
 
-  enum :event_type, create: 'create', update: 'update', discard: 'discard', restore: 'restore'
+  enum :event_type, { create: 'create',
+                      update: 'update',
+                      discard: 'discard',
+                      restore: 'restore' }, prefix: true, validate: true
 
-  validates :version_no, presence: true, numerically: { only_integer: true, greater_than: 0 }
+  validates :version_no, presence: true, numericality: { only_integer: true, greater_than: 0 }
   validates :event_type, presence: true, inclusion: { in: event_types.keys }
   validates :url, presence: true
 
diff --git a/backend/app/services/post_version_recorder.rb b/backend/app/services/post_version_recorder.rb
index 20f5c1e..052bacd 100644
--- a/backend/app/services/post_version_recorder.rb
+++ b/backend/app/services/post_version_recorder.rb
@@ -3,7 +3,7 @@ class PostVersionRecorder
     new(post:, event_type:, created_by_user:).record!
   end
 
-  def initialize post:, event_type:, created_user:
+  def initialize post:, event_type:, created_by_user:
     @post = post
     @event_type = event_type
     @created_by_user = created_by_user
@@ -23,7 +23,7 @@ class PostVersionRecorder
           title: attrs[:title],
           url: attrs[:url],
           thumbnail_base: attrs[:thumbnail_base],
-          tags: attrs[:url],
+          tags: attrs[:tags],
           parent: attrs[:parent],
           original_created_from: attrs[:original_created_from],
           original_created_before: attrs[:original_created_before],
diff --git a/backend/db/migrate/20260409123700_create_post_versions.rb b/backend/db/migrate/20260409123700_create_post_versions.rb
index f1c884e..b7a38d8 100644
--- a/backend/db/migrate/20260409123700_create_post_versions.rb
+++ b/backend/db/migrate/20260409123700_create_post_versions.rb
@@ -1,5 +1,17 @@
 class CreatePostVersions < ActiveRecord::Migration[8.0]
-  def change
+  class Post < ApplicationRecord
+    self.table_name = 'posts'
+  end
+
+  class PostTag < ApplicationRecord
+    self.table_name = 'post_tags'
+  end
+
+  class PostVersion < ApplicationRecord
+    self.table_name = 'post_versions'
+  end
+
+  def up
     create_table :post_versions do |t|
       t.references :post, null: false, foreign_key: true
       t.integer :version_no, null: false
@@ -19,62 +31,45 @@ class CreatePostVersions < ActiveRecord::Migration[8.0]
       t.check_constraint "event_type IN ('create', 'update', 'discard', 'restore')"
     end
 
-    reversible do |dir|
-      dir.up do
-        execute <<~SQL
-          INSERT INTO
-            post_versions(
-              post_id
-            , version_no
-            , event_type
-            , title
-            , url
-            , thumbnail_base
-            , tags
-            , parent_id
-            , original_created_from
-            , original_created_before
-            , created_at
-            , created_by_user_id)
-          SELECT
-            posts.id
-          , 1
-          , 'create'
-          , posts.title
-          , posts.url
-          , posts.thumbnail_base
-          , COALESCE(tag_snapshots.tags, '')
-          , posts.parent_id
-          , posts.original_created_from
-          , posts.original_created_before
-          , posts.created_at
-          , posts.uploaded_user_id
-          FROM
-            posts
-            LEFT JOIN
-              (
-                SELECT
-                  post_tags.post_id
-                , GROUP_CONCAT(tag_names.name ORDER BY tag_names.name SEPARATOR ' ') AS tags
-                FROM
-                  post_tags
-                  INNER JOIN
-                    tags
-                    ON
-                      tags.id = post_tags.tag_id
-                  INNER JOIN
-                    tag_names
-                    ON
-                      tag_names.id = tags.tag_name_id
-                WHERE
-                  post_tags.discarded_at IS NULL
-                GROUP BY
-                  post_tags.post_id
-                ) tag_snapshots
-              ON
-                tag_snapshots.post_id = posts.id
-        SQL
+    say_with_time 'Backfilling post_versions' do
+      Post.find_in_batches(batch_size: 500) do |posts|
+        post_ids = posts.map(&:id)
+
+        tag_names_by_post_id =
+            PostTag
+            .joins('INNER JOIN tags ON tags.id = post_tags.tag_id')
+            .joins('INNER JOIN tag_names ON tag_names.id = tags.tag_name_id')
+            .where(post_id: post_ids)
+            .where('post_tags.discarded_at IS NULL')
+            .where('tags.discarded_at IS NULL')
+            .where('tag_names.discarded_at IS NULL')
+            .pluck('post_tags.post_id', 'tag_names.name')
+            .each_with_object(Hash.new { |h, k| h[k] = [] }) do |(post_id, tag_name), h|
+              h[post_id] << tag_name
+            end
+
+        rows = posts.map do |post|
+          tags = tag_names_by_post_id[post.id].uniq.sort.join(' ')
+          { post_id: post.id,
+            version_no: 1,
+            event_type: 'create',
+            title: post.title,
+            url: post.url,
+            thumbnail_base: post.thumbnail_base,
+            tags:,
+            parent_id: post.parent_id,
+            original_created_from: post.original_created_from,
+            original_created_before: post.original_created_before,
+            created_at: post.created_at,
+            created_by_user_id: post.uploaded_user_id }
+        end
+
+        PostVersion.insert_all!(rows) if rows.present?
       end
     end
   end
+
+  def down
+    drop_table :post_versions
+  end
 end
diff --git a/backend/db/schema.rb b/backend/db/schema.rb
index 22541e2..34a6930 100644
--- a/backend/db/schema.rb
+++ b/backend/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2026_03_29_034700) do
+ActiveRecord::Schema[8.0].define(version: 2026_04_09_123700) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -132,6 +132,27 @@ ActiveRecord::Schema[8.0].define(version: 2026_03_29_034700) do
     t.index ["tag_id"], name: "index_post_tags_on_tag_id"
   end
 
+  create_table "post_versions", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "post_id", null: false
+    t.integer "version_no", null: false
+    t.string "event_type", null: false
+    t.string "title"
+    t.string "url", limit: 768, null: false
+    t.string "thumbnail_base", limit: 2000
+    t.text "tags", null: false
+    t.bigint "parent_id"
+    t.datetime "original_created_from"
+    t.datetime "original_created_before"
+    t.datetime "created_at", null: false
+    t.bigint "created_by_user_id"
+    t.index ["created_by_user_id"], name: "index_post_versions_on_created_by_user_id"
+    t.index ["parent_id"], name: "index_post_versions_on_parent_id"
+    t.index ["post_id", "version_no"], name: "index_post_versions_on_post_id_and_version_no", unique: true
+    t.index ["post_id"], name: "index_post_versions_on_post_id"
+    t.check_constraint "`event_type` in (_utf8mb4'create',_utf8mb4'update',_utf8mb4'discard',_utf8mb4'restore')"
+    t.check_constraint "`version_no` > 0"
+  end
+
   create_table "posts", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "title"
     t.string "url", limit: 768, null: false
@@ -362,6 +383,9 @@ ActiveRecord::Schema[8.0].define(version: 2026_03_29_034700) do
   add_foreign_key "post_tags", "tags"
   add_foreign_key "post_tags", "users", column: "created_user_id"
   add_foreign_key "post_tags", "users", column: "deleted_user_id"
+  add_foreign_key "post_versions", "posts"
+  add_foreign_key "post_versions", "posts", column: "parent_id"
+  add_foreign_key "post_versions", "users", column: "created_by_user_id"
   add_foreign_key "posts", "posts", column: "parent_id"
   add_foreign_key "posts", "users", column: "uploaded_user_id"
   add_foreign_key "settings", "users"