Kafka delivery modes¶

Choose your decoder to match the event source mapping. Lambda can deliver original binary data in SOURCE mode or convert registry-backed messages to JSON first.

Read JSON-mode messages¶

Use the kafka and logger imports from the JSON order example. This snippet runs in a function returning error.

Input

A JSON-mode Kafka record containing { "id": "ORD-123" }.

{
  "eventSource": "aws:kafka",
  "records": {
    "orders-0": [
      {
        "topic": "orders",
        "partition": 0,
        "offset": 1,
        "value": "eyJpZCI6Ik9SRC0xMjMifQ==",
        "valueSchemaMetadata": {
          "dataFormat": "JSON"
        },
        "headers": []
      }
    ]
  }
}

Code

appLog := logger.New(logger.WithServiceName("orders"))
consumer := kafka.New(kafka.Config{Value: &kafka.FieldConfig{Type: kafka.JSON}})
records, err := consumer.Deserialize(ctx, event)
if err != nil { return err }
value, err := records.Records[0].Value(ctx)
if err != nil { return err }
return appLog.Info("Order received", logger.Fields{"order": value})

event is the decoded input above.

Output

{
  "message": "Order received",
  "order": {
    "id": "ORD-123"
  }
}

This is a log excerpt; Logger also adds its level, timestamp, service and sampling rate. The order field contains the decoded value, not the Lambda handler response.

Select a mode¶

Configure key and value independently. Preserve the schema metadata supplied by Lambda; it is not a request to fetch a schema.

Things to know¶

• Keep the Kafka wrapper's raw event entry point when metadata presence and numeric tokens matter; typed SDK event models can lose that information.
• A registry schema ID does not make the library a schema registry client.
• Self-managed Kafka and MSK events both use the record decoding APIs. Deployment configuration belongs to the event source mapping.

Next steps¶

API and behavior notes · HTTP · Modules