Convex
A weekend of work, and real gaps remain.
A backend where your queries are functions that re-run automatically when their data changes, so the client stays live without you writing subscriptions.
Build reactivity explicitly. It is more code but it is understandable. STACK - Postgres, a small server, server-sent events THE HARD PART, NAMED - Convex knows which queries a write invalidates. You will have to say so yourself DOING IT BY HAND - Every query declares the tables and key ranges it depends on - Every write publishes which table and key it touched, through Postgres NOTIFY - The server maps that to the subscriptions affected and pushes to those clients only WHY NOT JUST REFETCH EVERYTHING - It works until it does not, and the failure is a thundering herd on a busy table - Declaring dependencies is twenty lines and avoids that entirely TRANSACTIONS - One database transaction per request, and no partial writes visible to a subscriber Include the dependency declaration, the NOTIFY bridge and the SSE fan-out.
What you lose
- Automatic invalidation, where the platform knows which queries a write affects and re-runs only those
- Transactional guarantees across functions without you reasoning about them
- A scheduler, file storage and search wired into the same model
If you would rather not build
- Postgres NOTIFY plus server-sent events
- Polling, which is fine more often than people admit
The escape hatch
open source · no votes, no paid placement
Supabase
$0Postgres with realtime subscriptions driven by replication.
supabase/supabasefree · open source
ElectricSQL
$0Syncs Postgres subsets to clients with conflict-free local writes.
electric-sql/electricfree · open source
Why this verdict
our own opinion · changed only by a person
52/100
Verdict kinda at 52. Reactivity by hand is entirely doable and the prompt shows the shape; automatic invalidation is what you are actually paying for.
History
tracked since 10 Aug 2026 · nothing is ever overwritten
Questions about Convex
answered from the record above
Is Convex free?
No — the plan we track is $25 a month. Professional from around $25 per member per month billed monthly, plus usage.
Can you replace Convex by building your own?
ALMOST. A weekend of work, and real gaps remain. Replacement score 52 out of 100, build time a weekend. Read what you lose before you decide.
How much does Convex cost?
$25 a month on Professional — $300 a year. Recorded 10 Aug 2026.
What do you lose by replacing Convex?
Automatic invalidation, where the platform knows which queries a write affects and re-runs only those; Transactional guarantees across functions without you reasoning about them; A scheduler, file storage and search wired into the same model. If any of those carry weight for you, keep paying.
Is there an open-source alternative to Convex?
Yes: Supabase, ElectricSQL. The prompt on this page is for when you want it your way instead.
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