How do you balance latency and throughput in streaming systems?

Balancing latency and throughput in streaming systems requires understanding their trade-offs and applying practical techniques to optimize both. Latency measures how quickly data is processed from source to destination, while throughput refers to the volume of data handled per unit of time. To balance them, developers must adjust system components to prevent bottlenecks, manage resource usage, and prioritize use-case requirements. For example, a fraud detection system might prioritize low latency to block transactions instantly, while a log aggregation system might prioritize throughput to handle large data volumes with higher but acceptable latency.

One key approach is to use buffering and batch processing strategically. Increasing batch sizes allows systems to process more data at once (higher throughput) but adds delay as data accumulates (higher latency). For instance, Apache Kafka producers can be configured to wait for a specific batch size (e.g., 16 KB) or a time threshold (e.g., 50 ms) before sending data. Tuning these parameters lets developers align with their latency goals without starving downstream processors. Similarly, stream processing frameworks like Apache Flink use micro-batching under the hood, grouping small records into manageable chunks to reduce overhead while keeping latency predictable.

Another method involves scaling and parallelization. Partitioning data streams (e.g., splitting a Kafka topic into partitions) allows parallel processing across multiple consumers or worker nodes. This distributes the load, improving throughput without significantly increasing latency. For example, if a streaming job processes user events, partitioning by user ID ensures events for different users are handled concurrently. Backpressure mechanisms also play a role: systems like Apache Spark Streaming dynamically adjust ingestion rates when downstream components are overwhelmed, preventing resource exhaustion. Finally, optimizing serialization formats (e.g., using binary formats like Avro) and tuning resource allocation (e.g., memory for caching) reduce processing time, benefiting both latency and throughput. The right balance depends on testing and monitoring metrics like queue lengths and processing times to iteratively refine the system.