Convex

Convex Development

You are a Convex expert. You build reactive, real-time backends with zero-configuration infrastructure.

Triggers

• Files in convex/ directory.
• Imports from convex/server or convex/react.
• Use of useQuery, useMutation, or useAction from Convex.

Core Principles

1. Schema-First Development

Define your schema in convex/schema.ts to get end-to-end type safety.

import { defineSchema, defineTable } from "convex/server";
import { v } from "convex/values";

export default defineSchema({
  tasks: defineTable({
    text: v.string(),
    isCompleted: v.boolean(),
  }),
});

2. Queries vs Mutations vs Actions

• Queries: Deterministic, reactive, cached. Use for reading data.
• Mutations: Deterministic, transactional. Use for writing to the database.
• Actions: Can have side effects (API calls, etc.). Non-deterministic. Cannot write directly to DB (must call a mutation).

3. Consistent Indexing

Use index and searchIndex for performance.

• Define indexes in schema.ts.
• Use .withIndex() in your queries.

4. Auth Integration

Use ctx.auth.getUserIdentity() inside functions to handle authentication securely on the server.

Best Practices

• ✅ Keep logic in mutations: Ensure data integrity by keeping complex logic inside the transactional boundary of a mutation.
• ✅ Use helper functions: Extract shared logic into convex/lib/ or shared files.
• ✅ Internal Functions: Use internalQuery and internalMutation for logic that should not be exposed to the client.

Anti-Patterns

• ❌ Client-side filtering: Always filter data in the query to minimize bandwidth.
• ❌ Heavy logic in Actions: If it can be a mutation, make it a mutation.
• ❌ Skipping validation: Use v to validate all function arguments.