Kafka streaming

Every committed transaction in EvidentSource is available as a Kafka record. You can consume this stream with any standard Kafka client.

Endpoints

Built-in (Milena)

Milena, EvidentSource’s Kafka-compatible broker, is built in and backed by SlateDB. It exposes:

• Sandbox Milena endpoint: kafkas://sandbox.evidentsource.com:9093
• Your deployment: typically port 9092 or 9093 behind your ALB

External bridge

If you’re bridging to an external Kafka (MSK, Confluent), configure the bridge container — see Kafka prerequisites.

Topic convention

• Per-database topic: evidentsource.<database>.events
• Keyed by <stream>:<subject>
• Values are CloudEvents JSON (default) or Avro/Protobuf (configurable)

Consuming

Use any Kafka client library. Bootstrap servers = the Milena or bridged endpoint. No special configuration beyond standard TLS/SASL for your environment.

from kafka import KafkaConsumer

consumer = KafkaConsumer(
    "evidentsource.todomvc.events",
    bootstrap_servers="sandbox.evidentsource.com:9093",
    security_protocol="SSL",
)
for msg in consumer:
    print(msg.key, msg.value)

Exactly-once semantics

EvidentSource commits transactions atomically to both the event store and the Milena log; Kafka consumers see exactly the events that were committed, in commit order.

When to subscribe via Kafka vs gRPC

Use Kafka when	Use gRPC SubscribeEvents when
Existing Kafka tooling / stream processors	Language has a good gRPC client
Long-lived pipelines	Short-lived consumers or browser clients
Integration with Kafka Connect / Streams	Filtering by stream / subject / type