{"id":2343,"date":"2026-05-27T18:15:57","date_gmt":"2026-05-27T18:15:57","guid":{"rendered":"https:\/\/tucumandevelopers.com\/index.php\/2026\/05\/27\/the-better-primary-key-a-guide-to-ulids-for-rails-developers\/"},"modified":"2026-05-27T18:15:57","modified_gmt":"2026-05-27T18:15:57","slug":"the-better-primary-key-a-guide-to-ulids-for-rails-developers","status":"publish","type":"post","link":"https:\/\/tucumandevelopers.com\/index.php\/2026\/05\/27\/the-better-primary-key-a-guide-to-ulids-for-rails-developers\/","title":{"rendered":"The Better Primary Key: A Guide to ULIDs for Rails Developers"},"content":{"rendered":"
\n
<\/div>\n
\n

In a previous article, I talked about Snowflake IDs<\/strong>. They are great, but they require a bit of configuration because you need to manage “Worker IDs.” <\/p>\n

If you want something simpler that gives you the same benefits – secure URLs and fast database sorting\u2014you should look at ULIDs<\/strong> (Universally Unique Lexicographically Sortable Identifiers).<\/p>\n

<\/a> Why not just use UUIDs? <\/h2>\n

Most developers switch from auto-incrementing integers to UUIDs<\/strong> because they want to hide their business volume. If your order ID is order\/550e8400-e29b...<\/code>, no one knows if you have 1 customer or 1 million.<\/p>\n

But UUIDs have a major problem: they are completely random.<\/strong>
When you insert millions of random UUIDs into a database, the “B-Tree” index gets fragmented and slow. Your database has to jump all over the hard drive to find where to put the new data.<\/p>\n

ULIDs fix this.<\/strong>
A ULID is 128 bits (just like a UUID), but the first part of the ID is a timestamp<\/strong>. This means ULIDs are chronological. They are unique like a UUID, but they sort like an Integer.<\/p>\n

Here is how to implement ULIDs in your Rails 8 app in 4 easy steps.<\/p>\n

<\/a> STEP 1: Install the Gem <\/h2>\n

We will use the ulid<\/code> gem to generate the strings. Add this to your Gemfile: <\/p>\n

\n
gem<\/span> \"ulid\"<\/span> <\/code><\/pre>\n
\n<\/p><\/div>\n<\/p><\/div>\n
Run bundle install<\/code> in your terminal.<\/p>\n
  <\/a> STEP 2: The ULID Concern <\/h2>\n
We want to make it very easy to add ULIDs to any model. The best way to do this is with a Concern<\/strong>. This code will ensure that every time we create a new record, a ULID is generated and assigned to the ID.<\/p>\n
Create a new file at app\/models\/concerns\/has_ulid.rb<\/code>: <\/p>\n
\n
# app\/models\/concerns\/has_ulid.rb<\/span> module<\/span> HasUlid<\/span> extend<\/span> ActiveSupport<\/span>::<\/span>Concern<\/span> included<\/span> do<\/span> # Before we save to the DB, generate the ULID<\/span> before_create<\/span> :set_ulid<\/span> end<\/span> private<\/span> def<\/span> set_ulid<\/span> # ULID.generate creates a string like: 01ARZ3NDEKTSV4RRFFQ69G5FAV<\/span> self<\/span>.<\/span>id<\/span> ||=<\/span> ULID<\/span>.<\/span>generate<\/span> end<\/span> end<\/span> <\/code><\/pre>\n
\n<\/p><\/div>\n<\/p><\/div>\n
  <\/a> STEP 3: The Migration <\/h2>\n
When you create a new model, you need to tell Rails that the id<\/code> is a string<\/code>, and you must disable the default auto-increment logic. <\/p>\n
\n
rails g model Product name:string <\/code><\/pre>\n
\n<\/p><\/div>\n<\/p><\/div>\n
Open the migration file and modify it like this: <\/p>\n
\n
# db\/migrate\/XXXXXXXXXXXXXX_create_products.rb<\/span> class<\/span> CreateProducts<\/span> <<\/span> ActiveRecord<\/span>::<\/span>Migration<\/span>[<\/span>8.0<\/span>]<\/span> def<\/span> change<\/span> # id: false stops the automatic integer ID<\/span> create_table<\/span> :products<\/span>,<\/span> id: <\/span>false<\/span> do<\/span> |<\/span>t<\/span>|<\/span> # We use string for ULID primary key<\/span> t<\/span>.<\/span>string<\/span> :id<\/span>,<\/span> primary_key: <\/span>true<\/span> t<\/span>.<\/span>string<\/span> :name<\/span> t<\/span>.<\/span>timestamps<\/span> end<\/span> end<\/span> end<\/span> <\/code><\/pre>\n
\n<\/p><\/div>\n<\/p><\/div>\n
  <\/a> STEP 4: Update the Model <\/h2>\n
Now, just include the concern we wrote in Step 2. <\/p>\n
\n
# app\/models\/product.rb<\/span> class<\/span> Product<\/span> <<\/span> ApplicationRecord<\/span> include<\/span> HasUlid<\/span> end<\/span> <\/code><\/pre>\n
\n<\/p><\/div>\n<\/p><\/div>\n
  <\/a> STEP 5: See it in action <\/h2>\n
Open your Rails console (bin\/rails c<\/code>) and create a few products: <\/p>\n
\n
Product<\/span>.<\/span>create<\/span>(<\/span>name: <\/span>\"Laptop\"<\/span>)<\/span> Product<\/span>.<\/span>create<\/span>(<\/span>name: <\/span>\"Monitor\"<\/span>)<\/span> Product<\/span>.<\/span>create<\/span>(<\/span>name: <\/span>\"Keyboard\"<\/span>)<\/span> # Check the IDs<\/span> Product<\/span>.<\/span>pluck<\/span>(<\/span>:id<\/span>)<\/span> # => [\"01HQV...\", \"01HQV...\", \"01HQV...\"]<\/span> <\/code><\/pre>\n
\n<\/p><\/div>\n<\/p><\/div>\n
If you look closely, the IDs all start with the same characters because they were created in the same minute. Because they are sortable, you can still run Product.order(:id)<\/code> and they will be in the correct chronological order!<\/p>\n
  <\/a> Why I like ULIDs for Rails <\/h2>\n
    \n
  1.  Better Performance:<\/strong> Because the IDs are sortable, PostgreSQL (or SQLite) can append them to the end of the index. This is much faster for “Write-Heavy” apps than random UUIDs.<\/li>\n
  2.  Readability:<\/strong> ULIDs use a special alphabet (Crockford’s Base32) that excludes confusing letters like “I”, “L”, and “O”. This makes them easier to read if a user has to type one in.<\/li>\n
  3.  No Setup:<\/strong> Unlike Snowflake IDs, you don’t need to configure server IDs or worker nodes. You just install the gem and go.<\/li>\n<\/ol>\n
    That’s pretty much it. It\u2019s a small architectural change that makes your app feel much more professional and scalable.<\/p>\n<\/p><\/div>\n<\/div>\n<\/div>\n<\/div>\n
    Fuente: Art\u00edculo original<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
    In a previous article, I talked about Snowflake IDs. They are great, but they require a bit of configuration because you need to manage “Worker IDs.” If you want something simpler that gives you the same benefits – secure URLs and fast database sorting\u2014you should look at ULIDs (Universally Unique Lexicographically Sortable Identifiers). Why not […]<\/p>\n","protected":false},"author":1,"featured_media":2342,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[41],"tags":[],"class_list":["post-2343","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-devto"],"jetpack_publicize_connections":[],"_links":{"self":[{"href":"https:\/\/tucumandevelopers.com\/index.php\/wp-json\/wp\/v2\/posts\/2343","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tucumandevelopers.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tucumandevelopers.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tucumandevelopers.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/tucumandevelopers.com\/index.php\/wp-json\/wp\/v2\/comments?post=2343"}],"version-history":[{"count":0,"href":"https:\/\/tucumandevelopers.com\/index.php\/wp-json\/wp\/v2\/posts\/2343\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/tucumandevelopers.com\/index.php\/wp-json\/wp\/v2\/media\/2342"}],"wp:attachment":[{"href":"https:\/\/tucumandevelopers.com\/index.php\/wp-json\/wp\/v2\/media?parent=2343"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tucumandevelopers.com\/index.php\/wp-json\/wp\/v2\/categories?post=2343"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tucumandevelopers.com\/index.php\/wp-json\/wp\/v2\/tags?post=2343"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}