Read rows safely
Create a `profiles` table query that returns `id` and `username` only for the signed-in user. Add a basic RLS policy note in comments.
Cloud / Knowledge library
Supabase
open-source backend platform on postgres
Why learn Supabase?
Supabase gives developers a fast backend stack (database, auth, storage, realtime, and serverless functions) so they can ship apps without building and operating each backend piece from scratch.
Where it came from
2020: Supabase launched publicly as an open-source Firebase alternative built on PostgreSQL. 2020: The company joined Y Combinator (S20), accelerating early adoption. 2021–2023: Core platform expanded with Auth, Storage, Realtime, and Edge Functions. 2024+: Focus increased on production workflows such as branching, observability, and AI-oriented Postgres use cases.
- 2020: Supabase launched publicly as an open-source Firebase alternative built on PostgreSQL.
- 2020: The company joined Y Combinator (S20), accelerating early adoption.
- 2021–2023: Core platform expanded with Auth, Storage, Realtime, and Edge Functions.
- 2024+: Focus increased on production workflows such as branching, observability, and AI-oriented Postgres use cases.
Build your understanding
Work through these exercises in order. Try the task before opening a reference.
- Create a `profiles` table query that returns `id` and `username` only for the signed-in user. Add a basic RLS policy note in comments.
- Implement sign-up, then insert a starter row into `todos` linked to the new user id. Handle and display both auth and insert errors.
- Subscribe to inserts on a `messages` table and render new messages live. Unsubscribe on component unmount to avoid leaks.
- Write an Edge Function that verifies JWT, validates JSON input, inserts into `orders`, and returns a safe error shape.
- Design a private bucket strategy for user uploads with signed URLs and RLS. Explain how anon and service keys are separated.
More ways to practice
Auth + insert flow
Implement sign-up, then insert a starter row into `todos` linked to the new user id. Handle and display both auth and insert errors.
Realtime mini-feed
Subscribe to inserts on a `messages` table and render new messages live. Unsubscribe on component unmount to avoid leaks.
Edge function guard
Write an Edge Function that verifies JWT, validates JSON input, inserts into `orders`, and returns a safe error shape.
Storage access design
Design a private bucket strategy for user uploads with signed URLs and RLS. Explain how anon and service keys are separated.
Documentation and sources
- Supabase Documentation (supabase.com)
- Supabase JavaScript Client Reference (supabase.com)
- Supabase GitHub Organization (github.com)
Catalog research notes
- Improved team workflows with stronger branching and preview environments.
- Expanded Edge Functions tooling in the CLI and dashboard.
- More AI-ready patterns using PostgreSQL + pgvector guidance and templates.
Connect the ideas
Explore next
Real World Example
Real-time Inventory Sync for Boutique Retail
A boutique retail chain managing high-turnover inventory across multiple physical locations and a web storefront.
The business problem
The business suffers from overselling items because their legacy database lacks a mechanism to push stock updates to client devices instantly, leading to manual reconciliation costs and customer dissatisfaction.
How this topic solves it
Supabase provides a managed Postgres database with built-in Realtime functionality, allowing the application to broadcast database changes directly to connected client sessions without polling.
- Initialize the project using the Supabase CLI to establish the local development environment.
- Define the inventory table schema within the Postgres database.
- Enable Realtime on the inventory table to track row-level changes.
- Implement a client-side subscription in the storefront application to listen for inventory updates.
- Apply Row Level Security policies to ensure only authorized staff can modify stock levels.
This diagram illustrates how database changes propagate to the client.
Stores inventory rows
Listens for DB changes
Displays live stock
Updates inventory
- POS System → writes update → Postgres DB
- Postgres DB → triggers change event → Realtime Engine
- Realtime Engine → broadcasts update → Storefront App
Implementation example
This code demonstrates subscribing to database changes in the Real-time Inventory Sync for Boutique Retail scenario to update the UI instantly when stock levels change.
const channel = supabase.channel('inventory-updates')
.on('postgres_changes', { event: 'UPDATE', schema: 'public', table: 'inventory' }, payload => {
console.log('Stock changed:', payload.new) // Update UI state dynamically
})
.subscribe()Expected business outcome
The storefront reflects accurate, live inventory counts across all user sessions, effectively eliminating the risk of overselling popular items.
Limitations and checks
Realtime subscriptions consume database connection slots and memory; developers must monitor the number of active channels to ensure the database remains performant under heavy concurrent load.