convex-backend

Define a query using the query function from the generated server module, specify args with Convex validators, and return data via ctx.db in the handler. Queries automatically re-run and push updates to subscribed clients when underlying data changes.

Use the mutation function with typed argument validators like v.string() and call ctx.db.insert or ctx.db.patch inside the handler. Mutations run transactionally, so all reads and writes in a single mutation either succeed or roll back together.

Queries read data reactively and auto-update subscribers, mutations write data with transactional guarantees, and actions run arbitrary server-side logic such as calling external APIs. Queries and mutations access the database directly, while actions invoke queries and mutations indirectly.

Convex supports authentication through Convex Auth and file uploads through its built-in storage system. The Skill covers implementing both patterns alongside reactive queries and mutations.

Convex may not fit when you need direct SQL access, existing relational database infrastructure, or long-running compute jobs beyond serverless limits. In those cases, a traditional database-backed API server is a better choice.