How would you optimize a Node.js application's JSON serialization performance for API responses with very large or very frequent payloads?

JSON.stringify() can become a measurable bottleneck for very large objects or extremely high-frequency serialization -- optimizations include using a schema-based fast serializer (like fastify's built-in JSON schema serialization, which precompiles a specialized serialization function ahead of time rather than using the generic, reflection-based JSON.stringify()), avoiding serializing unnecessary fields by shaping the response object beforehand, and, for very large responses, streaming JSON output incrementally rather than building and serializing one enormous in-memory object.

// Fastify's schema-based serialization compiles a specialized, much faster serializer
fastify.get('/users', {
  schema: {
    response: {
      200: {
        type: 'array',
        items: { type: 'object', properties: { id: { type: 'string' }, name: { type: 'string' } } },
      },
    },
  },
}, async () => getUsers());