1. Introduction
AI writes most of the code now, but you still choose the database. I focus on how fast I can try things for free, types and docs that AI handles well, and whether I buy auth and related features or build them myself.
To be clear, these five are not the same kind of thing. Supabase and Convex are BaaS types that include a DB, Neon is serverless Postgres at its core with surrounding features, MongoDB Atlas is the document DB itself, and Upstash Redis is a helper for cache and rate limiting. I compare them here by what I want to build.
2. Supabase
Supabase is a BaaS with Postgres + Auth + Storage + Realtime + Edge Functions. It is open source and I can self-host.
Free is $0 with DB 500MB, files 1GB, auth 50,000 MAU, and up to 2 active projects. It fits me when I want to launch a normal web app with auth as fast as possible. Pro is $25/month with DB 8GB, auth 100,000 MAU, and daily backups.
Reference: https://supabase.com/pricing
3. Neon
Neon is serverless Postgres at its core, now including Managed Better Auth, Object Storage, Functions, Realtime (Beta), and AI Gateway. Its strengths are branch-based DB copies, autoscaling, and extensions like pgvector.
Free is $0 with no time limit and no card required, 100 projects, 100 CU-hours/month per project, and storage 1GB/project. It fits me when I want to reuse my SQL and Postgres assets and spin up many preview environments. Launch is usage-based, with an official guide of $15/month and $0.106/CU-hour.
Reference: https://neon.com/pricing
4. MongoDB Atlas
MongoDB Atlas centers on a document DB, and I build auth and the API layer myself or combine it with App Services. It fits me when the data shape is still changing and I want document flexibility.
Free M0 is Free forever with 512MB and shared vCPU/RAM. I can consider Atlas Search and Vector Search on the same base for search use. Flex is $8-$30/month, and Dedicated starts at M10 from $0.08/hour.
Reference: https://www.mongodb.com/pricing
5. Upstash Redis
Upstash Redis is serverless Redis, a helper for cache, sessions, and rate limiting. It fits me when I keep my main DB and add it alongside to improve speed and control.
Free is $0 with 250MB, 500K commands per month, and 1 free DB. Per the official FAQ, a POST request alone issues a free Redis instantly with no signup, designed for AI agents to use right away. Usage is $0.2/100K commands, and fixed plans start at $10/month.
Reference: https://upstash.com/pricing
6. Convex
Convex is a reactive backend where I write queries, mutations, and actions in TypeScript. The DB is document-type and not SQL, with built-in realtime sync, file storage, scheduled execution, auth integration, and vector search. It fits me when I want realtime sync with React and TypeScript.
Free/Starter is $0 + usage for overages, with 1 million function calls per month, DB 0.5GB, files 1GB, and tokens for Chef AI app generation included. Professional is $25/developer/month with 25 million function calls per month and DB 50GB. It is open source and I can self-host.
Reference: https://www.convex.dev/pricing / https://docs.convex.dev/production/state/limits
7. How to Choose: Decide by What You Build
It is easier to work backward from what I build. For a normal web app with auth as fast as possible, Supabase; to reuse SQL and Postgres assets and mass-produce preview environments, Neon. For unsettled data shapes, MongoDB Atlas; to add cache and rate limiting to a separate main DB, Upstash Redis; for realtime sync with React and TypeScript, Convex.
8. Flowchart
For letting AI write it, I decide first whether I want Postgres types, document flexibility, or bundled surrounding features. That reduces rework. If requirements change, I just change the combination; I do not need to narrow it to one from the start.
9. Comparison Table
| Service | Type | Data model | Auth | Realtime | Free | Paid entry |
|---|---|---|---|---|---|---|
| Supabase | BaaS | Postgres | Built-in Auth | Realtime available | $0 with DB 500MB, files 1GB, auth 50,000 MAU, up to 2 projects | Pro $25/month with DB 8GB, auth 100,000 MAU, daily backups |
| Neon | Serverless Postgres + surrounding features | Postgres | Includes Managed Better Auth | Includes Realtime (Beta) | $0, no time limit and no card required, 100 projects, 100 CU-hours/month per project, storage 1GB/project | Launch is usage-based (official guide $15/month, $0.106/CU-hour) |
| MongoDB Atlas | Document DB | Document-type | Self-built or combined with App Services | — | M0 free with 512MB, shared vCPU/RAM | Flex $8-$30/month, Dedicated M10 from $0.08/hour |
| Upstash Redis | Serverless Redis, helper | Redis | Match to main system | Used for cache and similar | $0 with 250MB, 500K commands/month, 1 free DB | Usage $0.2/100K commands, fixed from $10/month |
| Convex | Reactive backend | Document-type, not SQL | Built-in auth integration | Built-in realtime sync | $0 + usage with 1M functions/month, DB 0.5GB, files 1GB | Professional $25/developer/month with 25M functions/month, DB 50GB |
10. Caveats
Supabase free pauses after 1 week with no access, so I check fit for left-alone test projects. Upstash is not a replacement for a main DB; I use it together with a main DB. Convex is not SQL, so I compare it with other options when I want to reuse existing SQL assets. Pricing and limits change, so I always confirm on the official sites.
11. Summary
The options narrow naturally based on whether I want BaaS, want to use Postgres fully, or prioritize changing shapes. If I need a helper, I add Upstash; if realtime sync is core, I consider Convex. The shortcut is to let AI touch the free tiers first, then decide by surrounding features and operational feel.
12. Sources
- https://supabase.com/pricing
- https://neon.com/pricing
- https://www.mongodb.com/pricing
- https://upstash.com/pricing
- https://www.convex.dev/pricing
- https://docs.convex.dev/production/state/limits
P.S. I wrote this article together with Muse (Fuwatchi), my AI agent. If you want to try Muse, I would appreciate it if you enter invite code EOA1TR. https://muse.ai/join``
