Caching strategies in Supabase

Introduction

Caching helps store data temporarily to make apps faster and reduce work on servers.

When your app shows the same data many times quickly.

When you want to reduce how often your database is asked for data.

When users expect fast loading times on your app.

When you want to save money by using fewer server resources.

Syntax

Supabase

cache.set(key, value, { ttl: seconds })
cache.get(key)
cache.delete(key)

cache.set saves data with a time limit (ttl).

cache.get retrieves saved data if it is still valid.

Examples

Saves user data for 60 seconds.

Supabase

cache.set('user_123', {name: 'Anna'}, { ttl: 60 })

Gets the saved user data if it is still in cache.

Supabase

const user = cache.get('user_123')

Removes the user data from cache immediately.

Supabase

cache.delete('user_123')

Sample Program

This example shows a simple cache using JavaScript Map. It stores user data for 30 seconds to avoid repeated database calls.

Supabase

import { createClient } from '@supabase/supabase-js'

const supabaseUrl = 'https://xyzcompany.supabase.co'
const supabaseKey = 'public-anonymous-key'
const supabase = createClient(supabaseUrl, supabaseKey)

// Simple cache object
const cache = new Map()

// Function to set cache with TTL
function cacheSet(key, value, ttl) {
  cache.set(key, { value, expires: Date.now() + ttl * 1000 })
}

// Function to get cache
function cacheGet(key) {
  const cached = cache.get(key)
  if (!cached) return null
  if (Date.now() > cached.expires) {
    cache.delete(key)
    return null
  }
  return cached.value
}

async function getUser(userId) {
  const cachedUser = cacheGet(userId)
  if (cachedUser) {
    console.log('Returning cached user')
    return cachedUser
  }

  const { data, error } = await supabase
    .from('users')
    .select('*')
    .eq('id', userId)
    .single()

  if (error) {
    console.error('Error fetching user:', error)
    return null
  }

  cacheSet(userId, data, 30) // Cache for 30 seconds
  console.log('Returning fresh user')
  return data
}

// Example usage
(async () => {
  const user1 = await getUser('123')
  console.log(user1)
  const user2 = await getUser('123')
  console.log(user2)
})()

Important Notes

Always set a time limit (TTL) to avoid stale data.

Clear cache when data changes to keep it fresh.

Use caching wisely to balance speed and accuracy.

Summary

Caching stores data temporarily to speed up apps.

Use TTL to control how long data stays in cache.

Check cache first before asking the database.

Practice

1. What is the main purpose of caching in Supabase applications?

easy

A. To store data temporarily and speed up data access

B. To permanently save all user data

C. To delete old data from the database

D. To encrypt data for security

Solution

1. Step 1: Understand caching basics

   Caching temporarily stores data to avoid repeated database calls.

2. Step 2: Identify caching purpose in Supabase

   It speeds up app performance by quickly providing stored data.

3. Final Answer:

   To store data temporarily and speed up data access -> Option A

4. Quick Check:

   Caching = Temporary storage for speed [OK]

Hint: Caching means temporary storage to speed up access [OK]

Common Mistakes:

• Thinking caching permanently saves data
• Confusing caching with encryption
• Believing caching deletes data

2. Which of the following is the correct way to set a cache TTL (time-to-live) in Supabase client code?

easy

A. cache.set('key', value, { ttl: 300 })

B. cache.set('key', value, ttl=300)

C. cache.set('key', value, timeout: 300)

D. cache.set('key', value, expire: 300)

Solution

1. Step 1: Review Supabase cache TTL syntax

   Supabase uses an options object with a ttl property to set time-to-live.

2. Step 2: Match correct syntax

   cache.set('key', value, { ttl: 300 }) uses { ttl: 300 } which is the correct way to specify TTL in seconds.

3. Final Answer:

   cache.set('key', value, { ttl: 300 }) -> Option A

4. Quick Check:

   TTL set with { ttl: seconds } object [OK]

Hint: TTL uses { ttl: seconds } object in cache.set [OK]

Common Mistakes:

• Using ttl=300 instead of { ttl: 300 }
• Using wrong property names like timeout or expire
• Passing TTL as a separate argument without object

3. Given this Supabase cache check code:

const cachedData = cache.get('user_123');
if (cachedData) {
  console.log('Cache hit:', cachedData);
} else {
  const data = await supabase.from('users').select('*').eq('id', 123);
  cache.set('user_123', data, { ttl: 600 });
  console.log('Cache miss, fetched:', data);
}

What will be logged if the cache already has data for 'user_123'?

medium

A. Cache miss, fetched: [new data]

B. Cache hit: [cached data]

C. Error: cache.get is not a function

D. No output

Solution

1. Step 1: Check cache.get return value

   If cache has data for 'user_123', cachedData is truthy.

2. Step 2: Follow code logic on cache hit

   Code logs 'Cache hit:' plus cachedData without fetching from database.

3. Final Answer:

   Cache hit: [cached data] -> Option B

4. Quick Check:

   Cache hit logs cached data [OK]

Hint: Cache hit means cachedData exists, logs cache hit [OK]

Common Mistakes:

• Assuming it fetches from database even if cache exists
• Confusing cache miss and hit outputs
• Expecting errors when cache is valid

4. You wrote this code to cache user data but it always fetches from the database:

const cached = cache.get('user_1');
if (!cached) {
  const data = await supabase.from('users').select('*').eq('id', 1);
  cache.set('user_1', data, { ttl: 300 });
}
console.log(cached);

What is the main issue causing the cache miss?

medium

A. TTL is too short to keep data

B. cache.get syntax is incorrect

C. You never update the cached variable after setting cache

D. Database query is wrong

Solution

1. Step 1: Analyze variable assignment

   Variable 'cached' is assigned once before cache.set, so it stays null.

2. Step 2: Understand cache update logic

   After setting cache, 'cached' is not updated to new data, so console.log shows null.

3. Final Answer:

   You never update the cached variable after setting cache -> Option C

4. Quick Check:

   cached variable must update after cache.set [OK]

Hint: Update cached variable after cache.set to avoid misses [OK]

Common Mistakes:

• Assuming cache.set updates cached variable automatically
• Blaming TTL without checking variable assignment
• Thinking cache.get syntax is wrong without error

5. You want to optimize a Supabase app by caching user profile data but ensure updates are reflected quickly. Which caching strategy is best?

hard

A. Cache data without TTL and manually clear cache daily

B. Use very long TTL (e.g., 24 hours) to minimize database calls

C. Never cache user profiles to avoid stale data

D. Use short TTL (e.g., 60 seconds) and refresh cache after updates

Solution

1. Step 1: Consider update frequency and freshness

   User profiles may change, so cache must refresh often to avoid stale data.

2. Step 2: Choose caching strategy balancing speed and freshness

   Short TTL with cache refresh after updates keeps data fresh and speeds access.

3. Final Answer:

   Use short TTL (e.g., 60 seconds) and refresh cache after updates -> Option D

4. Quick Check:

   Short TTL + refresh = fresh and fast cache [OK]

Hint: Short TTL plus refresh keeps cache fresh and fast [OK]

Common Mistakes:

• Using long TTL causing stale data
• Avoiding cache entirely losing speed benefits
• Not refreshing cache after updates