Hands On System Design - Distributed Systems Implementation

Hands On System Design - Distributed Systems Implementation

Day 145: Real-Time Stream Processing with Apache Flink

Complex Event Processing on Log Streams

Feb 27, 2026
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Your Processing System Just Got a Turbo Engine

Remember yesterday’s machine learning pipeline that predicted issues from historical log data? Today we’re adding something even more powerful: real-time stream processing that analyzes logs as they flow through your system, detecting complex patterns within milliseconds.

Think of Apache Flink as an incredibly fast assembly line worker who can examine thousands of items per second, spot patterns across multiple items, remember what they saw minutes ago, and trigger actions instantly. While your ML models work on historical data, Flink operates on live streams—catching fraud attempts, detecting system failures, and triggering alerts before issues escalate.


What Makes Stream Processing Different

Batch processing (what you did with Spark on Day 143) is like reading yesterday’s newspaper—you get complete information but it’s already old news. Stream processing is like watching live TV—you see events as they happen and can react immediately.

Real-world impact: When Uber detects surge pricing patterns, Netflix identifies streaming quality issues, or your bank catches fraudulent transactions mid-swipe, they’re using stream processing engines like Flink.

Core Concepts: Complex Event Processing

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