How I burned through Supabase's free egress limit (5GB 10.26GB) with polling and select=*

#supabase #nextjs #postgres #webdev

TL;DR

Supabase free plan: 5GB egress/month
My project: 10.26GB (205% over limit)
Root cause: 5-second polling × select('*') on a table with a 200,000-char text column
Fix: generated column flag + select column restriction + visibilitychange polling stop

What happened

My KOBO project (issue-finder) had a collection-queue-form component polling if_jobs every 5 seconds via select('*'). The table includes raw_input_text (up to 200K chars). Through Vercel Functions, every poll was shipping that full column downstream.

5s interval × 200,000 chars × hours of operation = GB gone

Noticed when I checked the Supabase dashboard on 2026-05-31.

Fix 1: Generated column as boolean flag

If I only need to know whether raw input exists, I don't need to ship the text:

ALTER TABLE if_jobs
ADD COLUMN has_raw_input boolean
  GENERATED ALWAYS AS (raw_input_text IS NOT NULL) STORED;

Fix 2: Narrow the select

// Before
const { data } = await supabase.from('if_jobs').select('*')

// After — list view only needs lightweight columns
const { data } = await supabase
  .from('if_jobs')
  .select('id, status, has_raw_input, created_at, updated_at')

Fix 3: Slow down polling + stop on hidden tab

useEffect(() => {
  let interval: ReturnType<typeof setInterval> | null = null
  const start = () => { interval = setInterval(fetch, 30_000) } // 5s → 30s
  const stop = () => { if (interval) clearInterval(interval) }
  document.addEventListener('visibilitychange', () =>
    document.hidden ? stop() : start()
  )
  start()
  return stop
}, [])