How to Reduce Cold Start Time in Supabase Edge Functions

1// BAD: Importing entire lodash (70KB+ bundled)
2import _ from 'npm:lodash'
3const result = _.pick(data, ['name', 'email'])
4
5// GOOD: Import only what you need
6import pick from 'npm:lodash.pick'
7const result = pick(data, ['name', 'email'])
8
9// BEST: Use native JavaScript instead of lodash
10const { name, email } = data
11const result = { name, email }

1import { corsHeaders } from '../_shared/cors.ts'
2
3// Keep the Supabase client at top level (it's lightweight)
4import { createClient } from 'npm:@supabase/supabase-js@2'
5
6Deno.serve(async (req) => {
7  if (req.method === 'OPTIONS') {
8    return new Response('ok', { headers: corsHeaders })
9  }
10
11  const { action } = await req.json()
12
13  // Lazy-load heavy dependencies only when needed
14  if (action === 'generate-pdf') {
15    const { default: PDFDocument } = await import('npm:pdfkit')
16    // Use PDFDocument...
17  }
18
19  if (action === 'send-email') {
20    const { Resend } = await import('npm:resend')
21    // Use Resend...
22  }
23
24  return new Response(JSON.stringify({ ok: true }), {
25    headers: { ...corsHeaders, 'Content-Type': 'application/json' },
26  })
27})

1// BAD: Top-level await adds to cold start time
2const supabase = createClient(
3  Deno.env.get('SUPABASE_URL')!,
4  Deno.env.get('SUPABASE_SERVICE_ROLE_KEY')!
5)
6const { data: config } = await supabase.from('config').select('*').single()
7
8// GOOD: Create client at top level but fetch data lazily
9const supabase = createClient(
10  Deno.env.get('SUPABASE_URL')!,
11  Deno.env.get('SUPABASE_SERVICE_ROLE_KEY')!
12)
13
14let cachedConfig: any = null
15
16async function getConfig() {
17  if (!cachedConfig) {
18    const { data } = await supabase.from('config').select('*').single()
19    cachedConfig = data
20  }
21  return cachedConfig
22}
23
24Deno.serve(async (req) => {
25  const config = await getConfig()
26  // Use config...
27})

1-- Enable pg_cron extension (run once in SQL Editor)
2create extension if not exists pg_cron;
3
4-- Schedule a ping every 5 minutes to keep the function warm
5select cron.schedule(
6  'keep-function-warm',
7  '*/5 * * * *',
8  $$
9  select
10    net.http_post(
11      url := 'https://<project-ref>.supabase.co/functions/v1/my-function',
12      headers := jsonb_build_object(
13        'Authorization', 'Bearer ' || current_setting('app.settings.service_role_key'),
14        'Content-Type', 'application/json'
15      ),
16      body := '{"ping": true}'::jsonb
17    );
18  $$
19);

1Deno.serve(async (req) => {
2  const start = performance.now()
3
4  // Your function logic here
5  const result = { message: 'Hello!' }
6
7  const duration = performance.now() - start
8  console.log(`Request processed in ${duration.toFixed(2)}ms`)
9
10  return new Response(JSON.stringify(result), {
11    headers: { 'Content-Type': 'application/json' },
12  })
13})