fastify-ata

Fastify plugin for ata-validator - JSON Schema validation powered by simdjson.

Drop-in replacement for Fastify's default ajv validator. Standard Schema V1 compatible.

Install

npm install fastify-ata

Usage

const fastify = require('fastify')()
const fastifyAta = require('fastify-ata')

fastify.register(fastifyAta)

fastify.post('/user', {
  schema: {
    body: {
      type: 'object',
      properties: {
        name: { type: 'string', minLength: 1 },
        age: { type: 'integer', minimum: 0 },
        role: { type: 'string', default: 'user' }
      },
      required: ['name']
    }
  }
}, (req, reply) => {
  // req.body.role === 'user' (default applied)
  reply.send({ ok: true, name: req.body.name })
})

fastify.listen({ port: 3000 })

All your existing JSON Schema route definitions work as-is.

Options

fastify.register(fastifyAta, {
  coerceTypes: true,       // convert "42" → 42 for integer fields
  removeAdditional: true,  // strip properties not in schema
})

Standalone Mode (Pre-compiled)

Drop-in replacement for @fastify/ajv-compiler/standalone. Same API.

const StandaloneValidator = require('fastify-ata/standalone')

// Build phase (once) - compile schemas to JS files
const app = fastify({
  schemaController: { compilersFactory: {
    buildValidator: StandaloneValidator({
      readMode: false,
      storeFunction(routeOpts, code) {
        fs.writeFileSync(generateFileName(routeOpts), code)
      }
    })
  }}
})

// Read phase (every startup) - load pre-compiled, near-zero compile time
const app = fastify({
  schemaController: { compilersFactory: {
    buildValidator: StandaloneValidator({
      readMode: true,
      restoreFunction(routeOpts) {
        return require(generateFileName(routeOpts))
      }
    })
  }}
})

Standard Schema V1

ata-validator natively implements Standard Schema V1 - the emerging standard for TypeScript-first schema libraries.

const { Validator } = require('ata-validator')
const v = new Validator(schema)

// Standard Schema V1 interface
const result = v['~standard'].validate(data)
// { value: data } on success
// { issues: [{ message, path }] } on failure

Works with Fastify v5's Standard Schema support, tRPC, TanStack Form, Drizzle ORM.

What it does

• Registers a custom validatorCompiler using ata-validator
• Applies default values, coerceTypes, removeAdditional during validation
• Caches compiled schemas (WeakMap) for reuse across routes
• Returns Fastify-compatible validation errors on invalid requests (400)
• Works with Fastify v4 and v5

Performance

Real-world HTTP benchmark (autocannon, 10 connections, 5s)

| Payload | ata | ajv | | |---|---|---|---| | 1 user (0.1KB) | 65.7K req/sec | 65.7K req/sec | equal | | 10 users (0.9KB) | 57.2K | 55.3K | +3% | | 50 users (4.6KB) | 36.0K | 33.8K | +6% | | 100 users (9.1KB) | 24.6K | 22.6K | +9% |

Where ata really shines

| Scenario | ata | ajv | | |---|---|---|---| | Serverless cold start (50 schemas) | 7.7ms | 96ms | 12.5x faster | | ReDoS protection (catastrophic pattern) | 0.3ms | 765ms | immune | | Batch NDJSON (10K items, multi-core) | 13.4M/sec | 5.1M/sec | 2.6x faster | | validate(obj) valid (isolated) | 68M ops/sec | 8M ops/sec | 8.5x faster | | validate(obj) invalid (isolated) | 17M ops/sec | 8M ops/sec | 2.1x faster | | validateJSON(str) valid | 3.0M ops/sec | 1.9M ops/sec | 1.6x faster | | Fastify startup (500 routes) | 46ms | 77ms (standalone) | 1.7x faster | | Schema compilation | 113K ops/sec | 818 ops/sec | 138x faster |

Things only ata can do

• RE2 regex engine - linear-time guaranteed, immune to ReDoS attacks
• Multi-core parallel validation - NDJSON batch at 12.5M items/sec
• Standard Schema V1 - native support, ajv doesn't have it
• 138x faster compilation - serverless cold starts, dynamic schemas

License

MIT