Supabase architecture (Postgres, Auth, Storage, Realtime, Edge Functions) - Mini Project: Build & Apply

Build a Simple Supabase Backend Architecture

📖 Scenario: You are creating a simple backend for a photo sharing app using Supabase. You will set up the main parts of Supabase architecture: a Postgres database table, authentication, storage for photos, realtime updates, and an edge function to process uploads.

🎯 Goal: Build a basic Supabase backend with a photos table in Postgres, enable user authentication, configure storage for photo files, set up realtime updates on new photos, and create an edge function to log uploads.

📋 What You'll Learn

Create a Postgres table called photos with columns id, user_id, and url

Enable authentication with email and password

Create a storage bucket called photo-uploads

Set up realtime subscription on the photos table

Write an edge function called logUpload that logs photo upload events

💡 Why This Matters

🌍 Real World

This project models a common backend architecture for apps that need user login, file storage, live updates, and serverless functions.

💼 Career

Understanding Supabase architecture is useful for junior backend developers and cloud engineers working with modern serverless platforms.

1

Create the Postgres photos table

Write the SQL command to create a table called photos with columns: id as a primary key UUID, user_id as UUID, and url as text.

Supabase

-- Your SQL command here

Hint

Use CREATE TABLE photos and define id as UUID primary key with default UUID generation.

2

Enable email and password authentication

Write the Supabase CLI command to enable authentication with email and password for your project.

Supabase

CREATE TABLE photos (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  user_id UUID NOT NULL,
  url TEXT NOT NULL
);

-- Your Supabase CLI command here

Hint

Use the command supabase auth enable email-password to enable email/password login.

3

Create a storage bucket called photo-uploads

Write the Supabase CLI command to create a storage bucket named photo-uploads.

Supabase

CREATE TABLE photos (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  user_id UUID NOT NULL,
  url TEXT NOT NULL
);

supabase auth enable email-password

-- Your Supabase CLI command here

Hint

Use supabase storage create-bucket photo-uploads to create the bucket.

4

Set up realtime subscription and edge function

Write the Supabase CLI commands to subscribe to realtime changes on the photos table and create an edge function called logUpload.

Supabase

CREATE TABLE photos (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  user_id UUID NOT NULL,
  url TEXT NOT NULL
);

supabase auth enable email-password

supabase storage create-bucket photo-uploads

-- Your Supabase CLI commands here

Hint

Use supabase realtime enable photos to enable realtime on the table and supabase functions new logUpload to create the edge function.

Practice

1. Which Supabase component is responsible for managing user sign-ups and logins?

easy

A. Storage

B. Postgres

C. Realtime

D. Auth

Solution

1. Step 1: Understand Supabase components

   Supabase has several parts: Postgres for data, Auth for users, Storage for files, Realtime for live updates, and Edge Functions for custom code.

2. Step 2: Identify user management part

   The component that handles user sign-ups, logins, and authentication is called Auth.

3. Final Answer:

   Auth -> Option D

4. Quick Check:

   User management = Auth [OK]

Hint: Auth means user login and signup system [OK]

Common Mistakes:

• Confusing Postgres with user management
• Thinking Storage handles users
• Mixing Realtime with authentication

2. Which of the following is the correct way to initialize Supabase client in JavaScript?

easy

A. const supabase = Supabase.create('url', 'anon_key');

B. const supabase = createClient('url', 'anon_key');

C. const supabase = supabaseClient('url', 'anon_key');

D. const supabase = new Supabase('url', 'anon_key');

Solution

1. Step 1: Recall Supabase client initialization syntax

   Supabase uses the function createClient(url, key) to create a client instance.

2. Step 2: Match correct syntax

   const supabase = createClient('url', 'anon_key'); matches the exact syntax: const supabase = createClient('url', 'anon_key');

3. Final Answer:

   const supabase = createClient('url', 'anon_key'); -> Option B

4. Quick Check:

   Use createClient() to initialize Supabase [OK]

Hint: Use createClient() function to start Supabase [OK]

Common Mistakes:

• Using new keyword with Supabase
• Calling wrong function names
• Mixing class and function syntax

3. Given this code snippet, what will be logged if a new row is inserted into the 'messages' table?

const subscription = supabase
  .from('messages')
  .on('INSERT', payload => {
    console.log('New message:', payload.new.text);
  })
  .subscribe();

medium

A. New message: [text of inserted row]

B. New message: undefined

C. Error: .subscribe() is not a function

D. No output, subscription does not listen to INSERT

Solution

1. Step 1: Understand Realtime subscription

   The code listens for INSERT events on the 'messages' table and logs the new row's text field.

2. Step 2: Analyze the callback behavior

   When a new row is inserted, payload.new contains the new row data, so payload.new.text is the inserted message text.

3. Final Answer:

   New message: [text of inserted row] -> Option A

4. Quick Check:

   Realtime INSERT event logs new row text [OK]

Hint: INSERT event payload.new has new row data [OK]

Common Mistakes:

• Expecting payload.old instead of payload.new
• Thinking .subscribe() is invalid
• Assuming no output on INSERT

4. You wrote this Edge Function to upload a file to Supabase Storage but it fails with a permission error. What is the likely cause?

export async function POST(request) {
  const supabase = createClient(SUPABASE_URL, SUPABASE_SERVICE_ROLE_KEY);
  const data = await request.formData();
  const file = data.get('file');
  const { error } = await supabase.storage.from('avatars').upload(file.name, file);
  if (error) return new Response(error.message, { status: 400 });
  return new Response('Upload successful');
}

medium

A. Storage upload requires user session, missing auth

B. The 'avatars' bucket does not exist

C. File object is not properly extracted from formData

D. Using SERVICE_ROLE_KEY in Edge Function is insecure and disabled

Solution

1. Step 1: Check authentication context for storage upload

   Storage upload requires a user session or proper auth context; using service role key alone in Edge Functions does not provide user session.

2. Step 2: Identify missing user session

   Without user session, storage upload is denied due to permission error.

3. Final Answer:

   Storage upload requires user session, missing auth -> Option A

4. Quick Check:

   Storage upload needs user auth session [OK]

Hint: Storage upload needs user session, not just service key [OK]

Common Mistakes:

• Assuming service role key works for storage upload
• Ignoring bucket existence
• Not checking file extraction from formData

5. You want to build a chat app using Supabase that updates messages live and stores user avatars. Which combination of Supabase components should you use?

hard

A. Auth for messages, Edge Functions for avatars, Storage for live updates

B. Realtime for messages and avatars, Postgres for user login

C. Postgres for messages, Storage for avatars, Realtime for live updates, Auth for user login

D. Storage for messages, Postgres for avatars, Edge Functions for live updates

Solution

1. Step 1: Identify storage needs

   Messages are structured data best stored in Postgres; avatars are files stored in Storage.

2. Step 2: Identify live update and user management

   Realtime provides live updates for messages; Auth manages user login.

3. Final Answer:

   Postgres for messages, Storage for avatars, Realtime for live updates, Auth for user login -> Option C

4. Quick Check:

   Use Postgres, Storage, Realtime, Auth together [OK]

Hint: Messages in Postgres, avatars in Storage, live with Realtime [OK]

Common Mistakes:

• Mixing Storage with live updates
• Using Realtime for file storage
• Confusing Auth with data storage