convex — quality + safety report

---
name: convex
description: "Convex reactive backend expert: schema design, TypeScript functions, real-time subscriptions, auth, file storage, scheduling, and deployment."
risk: safe
source: "https://docs.convex.dev"
date_added: "2026-02-27"
---

# Convex

You are an expert in Convex — the open-source, reactive backend platform where queries are TypeScript code. You have deep knowledge of schema design, function authoring (queries, mutations, actions), real-time data subscriptions, authentication, file storage, scheduling, and deployment workflows across React, Next.js, Angular, Vue, Svelte, React Native, and server-side environments.

## When to Use
- Use when building a new project with Convex as the backend
- Use when adding Convex to an existing React, Next.js, Angular, Vue, Svelte, or React Native app
- Use when designing schemas for a Convex document-relational database
- Use when writing or debugging Convex functions (queries, mutations, actions)
- Use when implementing real-time/reactive data patterns
- Use when setting up authentication with Convex Auth or third-party providers (Clerk, Auth0, etc.)
- Use when working with Convex file storage, scheduled functions, or cron jobs
- Use when deploying or managing Convex projects

## Core Concepts

Convex is a **document-relational** database with a fully managed backend. Key differentiators:

- **Reactive by default**: Queries automatically re-run and push updates to all connected clients when underlying data changes
- **TypeScript-first**: All backend logic — queries, mutations, actions, schemas — is written in TypeScript
- **ACID transactions**: Serializable isolation with optimistic concurrency control
- **No infrastructure to manage**: Serverless, scales automatically, zero config
- **End-to-end type safety**: Types flow from schema → backend functions → client hooks

### Function Types

| Type            | Purpose                   | Can Read DB    | Can Write DB      | Can Call External APIs | Cached/Reactive |
| :-------------- | :------------------------ | :------------- | :---------------- | :--------------------- | :-------------- |
| **Query**       | Read data                 | ✅             | ❌                | ❌                     | ✅              |
| **Mutation**    | Write data                | ✅             | ✅                | ❌                     | ❌              |
| **Action**      | Side effects              | via `runQuery` | via `runMutation` | ✅                     | ❌              |
| **HTTP Action** | Webhooks/custom endpoints | via `runQuery` | via `runMutation` | ✅                     | ❌              |

## Project Setup

### New Project (Next.js)

```bash
npx create-next-app@latest my-app
cd my-app && npm install convex
npx convex dev
```

### Add to Existing Project

```bash
npm install convex
npx convex dev
```

The `npx convex dev` command:

1. Prompts you to log in (GitHub)
2. Creates a project and deployment
3. Generates `convex/` folder for backend functions
4. Syncs functions to your dev deployment in real-time
5. Creates `.env.local` with `CONVEX_DEPLOYMENT` and `NEXT_PUBLIC_CONVEX_URL`

### Folder Structure

```
my-app/
├── convex/
│   ├── _generated/        ← Auto-generated (DO NOT EDIT)
│   │   ├── api.d.ts
│   │   ├── dataModel.d.ts
│   │   └── server.d.ts
│   ├── schema.ts          ← Database schema definition
│   ├── tasks.ts           ← Query/mutation functions
│   └── http.ts            ← HTTP actions (optional)
├── .env.local             ← CONVEX_DEPLOYMENT, NEXT_PUBLIC_CONVEX_URL
└── convex.json            ← Project config (optional)
```

## Schema Design

Define your schema in `convex/schema.ts` using the validator library:

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

export default defineSchema({
  users: defineTable({
    name: v.string(),
    email: v.string(),
    avatarUrl: v.optional(v.string()),
    tokenIdentifier: v.string(),
  })
    .index("by_token", ["tokenIdentifier"])
    .index("by_email", ["email"]),

  messages: defineTable({
    authorId: v.id("users"),
    channelId: v.id("channels"),
    body: v.string(),
    attachmentId: v.optional(v.id("_storage")),
  })
    .index("by_channel", ["channelId"])
    .searchIndex("search_body", { searchField: "body" }),

  channels: defineTable({
    name: v.string(),
    description: v.optional(v.string()),
    isPrivate: v.boolean(),
  }),
});
```

### Validator Types

| Validator                         | TypeScript Type       | Notes                                          |
| :-------------------------------- | :-------------------- | :--------------------------------------------- |
| `v.string()`                      | `string`              |                                                |
| `v.number()`                      | `number`              | IEEE 754 float                                 |
| `v.bigint()`                      | `bigint`              |                                                |
| `v.boolean()`                     | `boolean`             |                                                |
| `v.null()`                        | `null`                |                                                |
| `v.id("tableName")`               | `Id<"tableName">`     | Document reference                             |
| `v.array(v.string())`             | `string[]`            |                                                |
| `v.object({...})`                 | `{...}`               | Nested objects                                 |
| `v.optional(v.string())`          | `string \| undefined` |                                                |
| `v.union(v.string(), v.number())` | `string \| number`    |                                                |
| `v.literal("active")`             | `"active"`            | Literal types                                  |
| `v.bytes()`                       | `ArrayBuffer`         | Binary data                                    |
| `v.float64()`                     | `number`              | Explicit 64-bit float (used in vector indexes) |
| `v.any()`                         | `any`                 | Escape hatch                                   |

### Indexes

```typescript
// Single-field index
defineTable({ email: v.string() }).index("by_email", ["email"]);

// Compound index (order matters for range queries)
defineTable({
  orgId: v.string(),
  createdAt: v.number(),
}).index("by_org_and_date", ["orgId", "createdAt"]);

// Full-text search index
defineTable({ body: v.string(), channelId: v.id("channels") }).searchIndex(
  "search_body",
  {
    searchField: "body",
    filterFields: ["channelId"],
  },
);

// Vector search index (for AI/embeddings)
defineTable({ embedding: v.array(v.float64()), text: v.string() }).vectorIndex(
  "by_embedding",
  {
    vectorField: "embedding",
    dimensions: 1536,
  },
);
```

## Writing Functions

### Queries (Read Data)

Queries are reactive — clients automatically get updates when data changes.

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

// Simple query — list all tasks
export const list = query({
  args: {},
  handler: async (ctx) => {
    return await ctx.db.query("tasks").collect();
  },
});

// Query with arguments and filtering
export const getByChannel = query({
  args: { channelId: v.id("channels") },
  handler: async (ctx, args) => {
    return await ctx.db
      .query("messages")
      .withIndex("by_channel", (q) => q.eq("channelId", args.channelId))
      .order("desc")
      .take(50);
  },
});

// Query with auth check
export const getMyProfile = query({
  args: {},
  handler: async (ctx) => {
    const identity = await ctx.auth.getUserIdentity();
    if (!identity) return null;

    return await ctx.db
      .query("users")
      .withIndex("by_token", (q) =>
        q.eq("tokenIdentifier", identity.tokenIdentifier),
      )
      .unique();
  },
});

### Paginated Queries

Use cursor-based pagination for lists or infinite scroll UIs.

```typescript
import { query } from "./_generated/server";
import { paginationOptsValidator } from "convex/server";

export const listPaginated = query({
  args: {
    paginationOpts: paginationOptsValidator
  },
  handler: async (ctx, args) => {
    return await ctx.db
      .query("messages")
      .order("desc")
      .paginate(args.paginationOpts);
  },
});
```

### Mutations (Write Data)

Mutations run as ACID transactions with serializable isolation.

```typescript
import { mutation } from "./_generated/server";
import { v } from "convex/values";

// Insert a document
export const create = mutation({
  args: { text: v.string(), isCompleted: v.boolean() },
  handler: async (ctx, args) => {
    const taskId = await ctx.db.insert("tasks", {
      text: args.text,
      isCompleted: args.isCompleted,
    });
    return taskId;
  },
});

// Update a document
export const update = mutation({
  args: { id: v.id("tasks"), isCompleted: v.boolean() },
  handler: async (ctx, args) => {
    await ctx.db.patch(args.id, { isCompleted: args.isCompleted });
  },
});

// Delete a document
export const remove = mutation({
  args: { id: v.id("tasks") },
  handler: async (ctx, args) => {
    await ctx.db.delete(args.id);
  },
});

// Multi-document transaction (automatically atomic)
export const transferCredits = mutation({
  args: {
    fromUserId: v.id("users"),
    toUserId: v.id("users"),
    amount: v.number(),
  },
  handler: async (ctx, args) => {
    const fromUser = await ctx.db.get(args.fromUserId);
    const toUser = await ctx.db.get(args.toUserId);
    if (!fromUser || !toUser) throw new Error("User not found");
    if (fromUser.credits < args.amount) throw new Error("Insufficient credits");

    await ctx.db.patch(args.fromUserId, {
      credits: fromUser.credits - args.amount,
    });
    await ctx.db.patch(args.toUserId, {
      credits: toUser.credits + args.amount,
    });
  },
});
````

### Actions (External APIs & Side Effects)

Actions can call third-party services but cannot directly access the database — they must use `ctx.runQuery` and `ctx.runMutation`.

```typescript
import { action } from "./_generated/server";
import { v } from "convex/values";
import { api } from "./_generated/api";

export const sendEmail = action({
  args: { to: v.string(), subject: v.string(), body: v.string() },
  handler: async (ctx, args) => {
    // Call external API
    const response = await fetch("https://api.sendgrid.com/v3/mail/send", {
      method: "POST",
      headers: {
        Authorization: `Bearer ${process.env.SENDGRID_API_KEY}`,
        "Content-Type": "application/json",
      },
      body: JSON.stringify({
        personalizations: [{ to: [{ email: args.to }] }],
        from: { email: "noreply@example.com" },
        subject: args.subject,
        content: [{ type: "text/plain", value: args.body }],
      }),
    });

    if (!response.ok) throw new Error("Failed to send email");

    // Write result back to database via mutation
    await ctx.runMutation(api.emails.recordSent, {
      to: args.to,
      subject: args.subject,
      sentAt: Date.now(),
    });
  },
});

// Generate AI embeddings
export const generateEmbedding = action({
  args: { text: v.string(), documentId: v.id("documents") },
  handler: async (ctx, args) => {
    const response = await fetch("https://api.openai.com/v1/embeddings", {
      method: "POST",
      headers: {
        Authorization: `Bearer ${process.env.OPENAI_API_KEY}`,
        "Content-Type": "application/json",
      },
      body: JSON.stringify({
        model: "text-embedding-3-small",
        input: args.text,
      }),
    });

    const { data } = await response.json();
    await ctx.runMutation(api.documents.saveEmbedding, {
      documentId: args.documentId,
      embedding: data[0].embedding,
    });
  },
});
```

### HTTP Actions (Webhooks)

```typescript
import { httpRouter } from "convex/

… (truncated)