March 28, 2025 5 min read Data Architecture Series: EVENT_STREAM Home

Event Stream Data Architecture: From Logs to Real Time Decisions

Event streams are append only facts about what happened. They let systems react now and analyze later without coupling every service to every other service.

I use event streams when the business needs a durable timeline of what happened, not just a current row. I recommend designing the broker, schema, processors, lake storage, and serving projections as one governed path.

Facts in the order they happened

Facts in the order they happened Event stream data shown as a sequence over time. Facts in the order they happened 1 Observe Checkout, login,payment, shipment,or fraud signal 2 Capture Event key, schema,timestamp,payload, producer, 3 Use A replayable factthat downstreamsystems can react Common handles event_id key schema_id occurred_at

Event streams are most useful when consumers can replay the same facts and arrive at the same story.

How event streams drive reaction and replay

How event streams drive reaction and replay Event stream data moving from source action into operational and analytical uses. How event streams drive reaction and replay Source moment Payment isauthorized Captured data Payment event, key,schema, timestamp, andpayload Use 1Update orderstate Use 2Triggerfulfillment Use 3Replayincidents Use 4Build realtime metrics Event streams are most useful when consumers can replay the same facts and arrive at the samestory.

Event streams are most useful when consumers can replay the same facts and arrive at the same story.

Storage patterns I would expect

When I talk about "Storage patterns I would expect", I am checking whether Event Stream Data Architecture can be traced back, trusted, and used by someone making a decision.

Kafka, Kinesis, Event Hubs, Pub/Sub, Flink, Spark Structured Streaming, Druid, Pinot, ClickHouse, BigQuery, OpenSearch.

Useful cloud services

ProviderTypical services
AWSKinesis, MSK, Glue Streaming, Lambda, OpenSearch, Redshift.
AzureEvent Hubs, Stream Analytics, Data Explorer, Synapse.
Google CloudPub/Sub, Dataflow, BigQuery, Bigtable.

Public example worth knowing

I use "Public example worth knowing" to keep Event Stream Data Architecture grounded in a real system, because abstract patterns are too easy to agree with and too hard to operate.

LinkedIn Kafka is the reference example. Kafka was created at LinkedIn for data pipeline needs and became the industry default mental model for durable, replayable event streams.

A business example

I use "A business example" to keep Event Stream Data Architecture grounded in a real system, because abstract patterns are too easy to agree with and too hard to operate.

A checkout system emits order placed, payment captured, item packed, and shipment created. Stream jobs update customer search, fraud features, warehouse facts, and operational alerts independently.

Operational code example

When I show "Operational code example", I want the code in Event Stream Data Architecture to reveal the production decision, not just the syntax.

void handle(OrderEvent event) {
    if (processedEvents.exists(event.eventId())) return;
    if (event.schemaVersion() < 3) {
        deadLetter.publish(event, "unsupported schema");
        return;
    }

    orderProjection.apply(event.orderId(), event.eventType(), event.occurredAtEpochMs());
    processedEvents.save(event.eventId());
}

The handler ignores duplicate events, rejects old schemas, updates the projection, and records the event id. That is the minimum production shape for safe stream consumption.

What I would check first

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Written by Arunkumar Ganesan.

What I learnt is that event streams are powerful only when consumers can trust the contract and replay the past safely.

#DataArchitecture #DataEngineering #ETL #CloudArchitecture #EVENTSTREAM