MoonDB vs Convex: REST in Any Language vs a Reactive Runtime
Convex is a managed reactive database that runs your business logic (queries, mutations, actions) inside their TypeScript/JavaScript runtime, with live subscriptions baked in. It's excellent for collaborative TypeScript apps that need real-time updates everywhere. MoonDB takes a different stance: data is data, and your application code lives wherever you want it — Next.js, FastAPI, a Go service, a Rust CLI, or generated by an AI agent in any language. The API surface is plain REST + JSON schema. No proprietary runtime to learn.
Where they differ
| Capability | MoonDB | Convex |
|---|---|---|
| Backend code | None. CRUD is auto-generated from the schema. Custom logic lives in your app code. | Queries and mutations written in TypeScript inside Convex's runtime. |
| Client SDKs | Plain HTTP from any language. OpenAPI 3.0.3 for codegen. | TypeScript / JavaScript / React first; other languages have community clients. |
| Schema | Declarative JSON via PUT /v1/schema. Auto-diff, auto-migrate. |
TypeScript schema.ts file with Convex schema helpers. |
| Real-time | Not yet (REST + cursor pagination) | Live queries — every query is a subscription by default |
| Auth | Built-in email/password + JWKS for external IdPs | Built-in via Clerk, Auth0, Custom JWT |
| File storage | R2-backed, schema-integrated type: "file" column |
Convex File Storage (built-in) |
| AI features | Schema-defined AI endpoints (text + image models, no API keys to manage) | Vector search; you wire up models yourself |
| Agent integration | Native MCP server, 14 tools, /v1/llm-context, per-project .cursorrules |
No first-party MCP |
| Lock-in | Plain REST + standard HTTP. Port off with a simple shim. | Logic lives in Convex's runtime. Migrating off is a rewrite. |
| Pricing | Free → $9 → $29 → $99/mo with hard quotas | Free → $25/mo → usage-based |
When Convex is the right call
- Real-time collaboration is core (multiplayer apps, dashboards, live cursors). Convex's reactive queries beat polling.
- TypeScript-first team that's happy keeping mutations and queries in one TS file alongside the schema.
- Strong consistency with optimistic UI — Convex's runtime handles transactional mutations across multiple tables natively.
- Vector search tightly integrated with the database.
When MoonDB is the right call
- Language-agnostic. Generated app code in Next.js, Python, Go, Rust — all of it talks plain HTTP to
/p/{id}/api/.... - AI agents writing the backend. A JSON schema is something Cursor / Claude can produce and migrate; a TypeScript Convex schema is something the agent has to learn the API for first.
- No proprietary runtime. Your business logic stays in your existing service (Express, FastAPI, Rails) where you can test it, debug it, and port it.
- You don't need real-time yet. Polling and pagination cover most CRUD apps; you can add a WebSocket layer later if you outgrow MoonDB's REST surface.
Migration sketch
Convex schema.ts tables map directly to MoonDB tables. Convex field types
(v.string(), v.number(), v.id("users")) map to
string, int/float, and ref users.
Convex queries become REST GET /api/{table}?filter=.... Convex mutations
become POST / PATCH / DELETE with the same filter
semantics. The hard part of a migration is not the data — it's deciding
where your real-time logic lives now (a WebSocket server, polling, or push from your
own backend service).