Convex Guidelines

Function Syntax

ALWAYS use the new function syntax with args, returns, and handler:

import { query } from "./_generated/server";
import { v } from "convex/values";

export const f = query({
  args: { name: v.string() },
  returns: v.string(),
  handler: async (ctx, args) => {
    return "Hello " + args.name;
  },
});

HTTP Endpoints

import { httpRouter } from "convex/server";
import { httpAction } from "./_generated/server";

const http = httpRouter();
http.route({
  path: "/echo",
  method: "POST",
  handler: httpAction(async (ctx, req) => {
    const body = await req.bytes();
    return new Response(body, { status: 200 });
  }),
});

Validators

Discriminated Unions

v.union(
  v.object({ kind: v.literal("error"), errorMessage: v.string() }),
  v.object({ kind: v.literal("success"), value: v.number() }),
)

Function Registration

• Public: query, mutation, action – exposed to internet
• Internal: internalQuery, internalMutation, internalAction – only callable by other Convex functions

ALWAYS include argument AND return validators. Use returns: v.null() if no return value.

Function Calling

• ctx.runQuery – call query from query/mutation/action
• ctx.runMutation – call mutation from mutation/action
• ctx.runAction – call action from action (only for crossing runtimes V8↔Node)

Use FunctionReference (from api or internal objects), NOT the function directly:

// Correct
await ctx.runQuery(api.example.f, { name: "Bob" });
// Wrong
await ctx.runQuery(f, { name: "Bob" });

For same-file calls, add type annotation to avoid circularity:

const result: string = await ctx.runQuery(api.example.f, { name: "Bob" });

Function References

• api.path.to.functionName – public functions
• internal.path.to.functionName – internal functions

File-based routing: convex/messages/access.ts → api.messages.access.functionName

Schema

Define in convex/schema.ts:

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

export default defineSchema({
  messages: defineTable({
    channelId: v.id("channels"),
    content: v.string(),
  }).index("by_channel", ["channelId"]),
});

System fields auto-added: _id (v.id(tableName)), _creationTime (v.number())

Index naming: include all fields → by_field1_and_field2

Queries

• Do NOT use filter() – use withIndex() instead
• No .delete() – collect results, iterate, call ctx.db.delete(row._id)
• .unique() for single document (throws if multiple match)
• Default order: ascending _creationTime

const messages = await ctx.db
  .query("messages")
  .withIndex("by_channel", (q) => q.eq("channelId", channelId))
  .order("desc")
  .take(10);

Full Text Search

const messages = await ctx.db
  .query("messages")
  .withSearchIndex("search_body", (q) =>
    q.search("body", "hello hi").eq("channel", "#general"),
  )
  .take(10);

Pagination

import { paginationOptsValidator } from "convex/server";

export const list = query({
  args: { paginationOpts: paginationOptsValidator, author: v.string() },
  handler: async (ctx, args) => {
    return await ctx.db
      .query("messages")
      .withIndex("by_author", (q) => q.eq("author", args.author))
      .order("desc")
      .paginate(args.paginationOpts);
  },
});

Returns: { page, isDone, continueCursor }

Mutations

• ctx.db.patch(id, fields) – shallow merge
• ctx.db.replace(id, doc) – full replace

Actions

Add "use node"; at top for Node.js modules. Actions have NO ctx.db access.

"use node";
import { action } from "./_generated/server";

export const myAction = action({
  args: {},
  returns: v.null(),
  handler: async (ctx, args) => {
    // Use ctx.runQuery/ctx.runMutation for DB access
    return null;
  },
});

Scheduling

Crons

import { cronJobs } from "convex/server";
import { internal } from "./_generated/api";

const crons = cronJobs();
crons.interval("job name", { hours: 2 }, internal.crons.myFunc, {});
export default crons;

Only use crons.interval or crons.cron. NOT crons.hourly/daily/weekly.

File Storage

const url = await ctx.storage.getUrl(storageId); // Returns signed URL or null

// Get metadata via system table
const metadata = await ctx.db.system.get(storageId);
// Returns: { _id, _creationTime, contentType?, sha256, size }

TypeScript

• Use Id<'tableName'> from ./_generated/dataModel for typed IDs
• as const for string literals in unions
• Add @types/node to package.json when using Node.js modules

import { Id } from "./_generated/dataModel";
const idToName: Record<Id<"users">, string> = {};

Examples

• Chat app with AI: See chat-app-example.md