Supabase Load & Scale

Read replicas let you route read-heavy queries (dashboards, reports, search) to replica databases while keeping writes on the primary. Supabase uses Supavisor (their pgBouncer replacement) for connection pooling with two modes: transaction (default, shares connections between requests) and session (holds a connection per client session, needed for prepared statements).

Configure the Read Replica Client

// lib/supabase.ts
import { createClient } from '@supabase/supabase-js'
import type { Database } from './database.types'

// Primary client — handles all writes and real-time subscriptions
export const supabase = createClient<Database>(
  process.env.SUPABASE_URL!,
  process.env.SUPABASE_ANON_KEY!
)

// Read replica client — use for analytics, dashboards, search
// The read replica URL is available in Dashboard > Settings > Database
export const supabaseReadOnly = createClient<Database>(
  process.env.SUPABASE_READ_REPLICA_URL!,  // e.g., https://<project-ref>-ro.supabase.co
  process.env.SUPABASE_ANON_KEY!,          // same anon key works for replicas
  {
    db: { schema: 'public' },
    // Replicas may have slight lag (typically <100ms)
    // Do NOT use for reads-after-writes in the same request
  }
)

// Server-side admin client with connection pooling via Supavisor
// Use the pooled connection string (port 6543) instead of direct (port 5432)
export const supabaseAdmin = createClient<Database>(
  process.env.SUPABASE_URL!,
  process.env.SUPABASE_SERVICE_ROLE_KEY!,
  {
    auth: { autoRefreshToken: false, persistSession: false },
    db: { schema: 'public' },
  }
)

Direct Postgres Connections via Supavisor Pooling

# Transaction mode (default, port 6543) — best for serverless/short-lived connections
# Shares connections across clients. Cannot use prepared statements.
psql "postgresql://postgres.[project-ref]:[password]@aws-0-us-east-1.pooler.supabase.com:6543/postgres"

# Session mode (port 5432 via pooler) — needed for prepared statements, LISTEN/NOTIFY
# One-to-one connection mapping per client.
psql "postgresql://postgres.[project-ref]:[password]@aws-0-us-east-1.pooler.supabase.com:5432/postgres"

# Direct connection (no pooling) — for migrations and admin tasks only
psql "postgresql://postgres:[password]@db.[project-ref].supabase.co:5432/postgres"

Route Queries to the Right Target

// services/analytics.ts
import { supabaseReadOnly } from '../lib/supabase'

// Heavy analytics queries go to the read replica
export async function getDashboardMetrics(orgId: string) {
  const { data, error } = await supabaseReadOnly
    .from('events')
    .select('event_type, count:id.count()')
    .eq('org_id', orgId)
    .gte('created_at', new Date(Date.now() - 24 * 60 * 60 * 1000).toISOString())

  if (error) throw new Error(`Dashboard query failed: ${error.message}`)
  return data
}

// services/orders.ts
import { supabase } from '../lib/supabase'

// Writes always go to the primary
export async function createOrder(order: OrderInsert) {
  const { data, error } = await supabase
    .from('orders')
    .insert(order)
    .select('id, status, total, created_at')
    .single()

  if (error) throw new Error(`Order creation failed: ${error.message}`)
  return data
}

Monitor Connection Pool Usage

-- Check active connections by source (run in SQL Editor)
SELECT
  usename,
  application_name,
  client_addr,
  state,
  count(*) AS connections
FROM pg_stat_activity
WHERE datname = 'postgres'
GROUP BY usename, application_name, client_addr, state
ORDER BY connections DESC;

-- Check connection limits for your compute tier
SHOW max_connections;
-- Micro: 60, Small: 90, Medium: 120, Large: 160, XL: 240, 2XL: 380, 4XL: 480

Step 2 — Compute Upgrades, CDN for Storage, and Edge Function Regions

Compute Size Selection Guide

# Upgrade compute via CLI (requires Pro plan)
supabase projects update --experimental --compute-size small  # or medium, large, xl, 2xl, 4xl

# Check current compute size
supabase projects list

CDN Caching for Storage Buckets

Public buckets are automatically served through Supabase's CDN. Optimize cache behavior with proper headers and transforms.

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

const supabase = createClient(
  process.env.SUPABASE_URL!,
  process.env.SUPABASE_ANON_KEY!
)

// Upload with cache-control headers for CDN optimization
async function uploadPublicAsset(
  bucket: string,
  path: string,
  file: File
) {
  const { data, error } = await supabase.storage
    .from(bucket)
    .upload(path, file, {
      cacheControl: '31536000',  // 1 year cache for immutable assets
      upsert: false,             // prevent accidental overwrites
      contentType: file.type,
    })

  if (error) throw new Error(`Upload failed: ${error.message}`)

  // Get the CDN-cached public URL
  const { data: { publicUrl } } = supabase.storage
    .from(bucket)
    .getPublicUrl(path, {
      transform: {
        width: 800,        // Image transforms are cached at the CDN edge
        quality: 80,
        format: 'webp',
      },
    })

  return { path: data.path, publicUrl }
}

// Bust cache by uploading to a new path (content-addressed)
import { createHash } from 'crypto'

async function uploadVersionedAsset(bucket: string, file: Buffer, ext: string) {
  const hash = createHash('sha256').update(file).digest('hex').slice(0, 12)
  const path = `assets/${hash}.${ext}`

  const { error } = await supabase.storage
    .from(bucket)
    .upload(path, file, {
      cacheControl: '31536000',
      upsert: false,
    })

  if (error && error.message !== 'The resource already exists') {
    throw new Error(`Versioned upload failed: ${error.message}`)
  }

  return supabase.storage.from(bucket).getPublicUrl(path).data.publicUrl
}

Edge Function Regional Deployment

# Deploy to a specific region (closer to your users)
supabase functions deploy my-function --region us-east-1
supabase functions deploy my-function --region eu-west-1
supabase functions deploy my-function --region ap-southeast-1

# List available regions
supabase functions list

# Deploy all functions to a region
supabase functions deploy --region us-east-1

// supabase/functions/geo-router/index.ts
// Edge Function that runs in the region closest to the user
import { createClient } from 'https://esm.sh/@supabase/supabase-js@2'

Deno.serve(async (req) => {
  const supabase = createClient(
    Deno.env.get('SUPABASE_URL')!,
    Deno.env.get('SUPABASE_SERVICE_ROLE_KEY')!
  )

  // Edge Functions automatically run in the nearest region
  // Use this for latency-sensitive operations
  const { data, error } = await supabase
    .from('products')
    .select('id, name, price')
    .eq('region', req.headers.get('x-region') ?? 'us')
    .limit(20)

  if (error) {
    return new Response(JSON.stringify({ error: error.message }), { status: 500 })
  }

  return new Response(JSON.stringify(data), {
    headers: {
      'Content-Type': 'application/json',
      'Cache-Control': 'public, max-age=60',  // CDN caches the response
    },
  })
})

Step 3 — Database Table Partitioning

See table partitioning patterns for range partitioning by date, automated partition creation via pg_cron, SDK query patterns with partition key filters, and partition drop for data retention.

Output

• Read replica client configured for analytics/dashboard queries, primary for writes
• Connection pooling mode selected (transaction vs session) with correct port
• Compute tier matched to traffic requirements
• Storage uploads optimized with CDN cache headers and image transforms
• Edge Functions deployed to the region closest to users
• Large tables partitioned by date range with automated partition management
• Data retention policy via partition drops

Error Handling

Examples

Quick Connection Pool Check

# Check how many connections are in use right now
psql "$DATABASE_URL" -c "SELECT count(*) AS active_connections FROM pg_stat_activity WHERE state = 'active';"

Switch an Existing Table to Partitioned

-- You cannot ALTER an existing table to be partitioned.
-- Instead: create partitioned table, migrate data, swap names.

-- 1. Create new partitioned table
CREATE TABLE public.events_partitioned (LIKE public.events INCLUDING ALL)
  PARTITION BY RANGE (created_at);

-- 2. Create partitions for existing data range
CREATE TABLE public.events_p_2025_01 PARTITION OF public.events_partitioned
  FOR VALUES FROM ('2025-01-01') TO ('2025-02-01');
-- ... more partitions

-- 3. Copy data (do this during low traffic)
INSERT INTO public.events_partitioned SELECT * FROM public.events;

-- 4. Swap tables in a transaction
BEGIN;
  ALTER TABLE public.events RENAME TO events_old;
  ALTER TABLE public.events_partitioned RENAME TO events;
COMMIT;

-- 5. Verify, then drop old table
DROP TABLE public.events_old;

Test Read Replica Lag

import { supabase, supabaseReadOnly } from '../lib/supabase'

async function measureReplicaLag() {
  // Write to primary
  const { data: written } = await supabase
    .from('health_checks')
    .insert({ timestamp: new Date().toISOString() })
    .select('id, timestamp')
    .single()

  // Immediately read from replica
  const start = Date.now()
  let found = false

  while (!found && Date.now() - start < 5000) {
    const { data } = await supabaseReadOnly
      .from('health_checks')
      .select('id')
      .eq('id', written!.id)
      .maybeSingle()

    if (data) {
      found = true
      console.log(`Replica lag: ${Date.now() - start}ms`)
    } else {
      await new Promise(r => setTimeout(r, 10))
    }
  }

  if (!found) console.warn('Replica lag exceeds 5 seconds')
}

Resources

• Supabase Read Replicas
• Supabase Connection Pooling (Supavisor)
• Supabase Compute Add-ons
• Supabase Storage CDN
• Supabase Edge Functions
• PostgreSQL Table Partitioning

Next Steps

For reliability patterns (circuit breakers, offline queues, graceful degradation), see supabase-reliability-patterns.