midApache Spark
Explain Fault Tolerance in Spark Streaming.
Updated May 5, 2026
Short answer
Spark Streaming uses Checkpointing and Write-Ahead Logs (WAL) to ensure fault tolerance.
Deep explanation
Checkpointing saves the state and metadata to reliable storage (HDFS/S3). WAL records incoming data to a log before processing.
Real-world example
A 24/7 financial monitor that must not lose a single event if a server reboots.
Common mistakes
- Not enabling WAL when using S3 as a source, leading to data loss on failure.
Follow-up questions
- What is Structured Streaming?