# KafkaRequest

**Kind:** Interface

**Source:** [`packages/microservices/serializers/kafka-request.serializer.ts`](https://github.com/nestjs/nest/blob/master/packages/microservices/serializers/kafka-request.serializer.ts#L10)

**Part of:** [Microservices](subsystem-packages-microservices)

`KafkaRequest` defines the normalized message shape consumed by the Kafka request serializer. It separates the Kafka message key, payload value, and headers so transport-specific metadata can be preserved when publishing or handling messages.

## Properties

| Property | Type |
|---|---|
| `key` | `Buffer | string | null` |
| `value` | `T` |
| `headers` | `Record<string, any>` |

## Diagram

```mermaid
graph LR
  Request[KafkaRequest<T>]
  Key[key: Buffer | string | null]
  Value[value: T]
  Headers[headers: Record<string, any>]

  Request --> Key
  Request --> Value
  Request --> Headers
```

## Usage

```ts
import { KafkaRequest } from './kafka-request.serializer';

interface UserCreatedEvent {
  userId: string;
  email: string;
}

const request: KafkaRequest<UserCreatedEvent> = {
  key: 'user-123',
  value: {
    userId: 'user-123',
    email: 'user@example.com',
  },
  headers: {
    correlationId: 'req-8f2a',
    eventType: 'user.created',
  },
};

// Pass `request` to the Kafka serializer or client publish operation.
```

## AI Coding Instructions

- Use `key` for Kafka partitioning; provide a stable string or `Buffer` when related messages must remain ordered.
- Set `key` to `null` when no partitioning key is required; do not use `undefined` unless the surrounding API explicitly supports it.
- Keep `value` strongly typed with `KafkaRequest<T>` so event payload contracts are preserved.
- Store transport metadata such as correlation IDs, tracing values, and event types in `headers`.
- Ensure header values are compatible with the configured Kafka client serialization behavior before publishing.

## Relationships

- IMPORTS → `isNil`
- IMPORTS → `isObject`
- IMPORTS → `isPlainObject`
- IMPORTS → `isString`
- IMPORTS → `isUndefined`