Convex is an open-source reactive database designed to simplify building dynamic, live-updating web applications. Unlike traditional backend stacks that require stitching together a database, server framework, caching layer, and real-time infrastructure, Convex provides all of these as a single integrated platform. Developers write server-side logic as pure TypeScript functions that the Convex runtime executes with ACID transactions and strong consistency guarantees.

Reactive Data Layer

The core differentiator of Convex is its reactive query model. Client applications subscribe to queries, and the Convex runtime automatically pushes updated results whenever the underlying data changes. This eliminates the need to manually implement WebSocket connections, polling, or cache invalidation. The React client library (convex/react) provides hooks like useQuery and useMutation that integrate seamlessly with React component lifecycles, making real-time UIs trivial to build.

Server Functions

Convex organizes backend logic into three types of functions: queries (read-only, cached, reactive), mutations (read-write, transactional), and actions (for calling external APIs and performing side effects). All functions are written in TypeScript and benefit from end-to-end type safety — the schema definition generates types that flow through to client code. Functions run in a sandboxed JavaScript environment with deterministic execution for queries and mutations.

Built-In Features

Beyond the database and functions, Convex includes file storage, scheduled functions (cron jobs), full-text search, and vector search out of the box. The platform also provides authentication integration with providers like Clerk and Auth0, HTTP endpoints for webhooks, and a dashboard for monitoring and debugging. The built-in schema validation uses a Zod-like validator API to enforce document structure at write time.

Self-Hosting and Deployment

The Convex backend is open-source under the Business Source License and can be self-hosted using Docker or prebuilt binaries. It works with PostgreSQL (including Neon), SQLite, and other storage backends. The self-hosted version includes the dashboard and CLI. For managed hosting, the Convex cloud platform offers a generous free tier suitable for side projects and small applications, with automatic scaling for production workloads.

Developer Experience

The Convex CLI (npx convex dev) provides a local development workflow with hot-reloading of server functions. Schema changes are applied with automatic migrations. The TypeScript-first approach means IDE autocompletion works across the full stack, and type errors are caught at compile time rather than runtime.