BigData / Apache Hudi Interview Questions
What is the difference between optimistic and non-blocking concurrency control in Hudi?
Hudi's original concurrency model is Optimistic Concurrency Control (OCC): multiple writers can attempt writes concurrently, but conflicts (two writers touching the same file group) are detected at commit time, and one of the conflicting writers fails and must retry — typically coordinated with an external lock provider like Zookeeper or a DynamoDB-based lock.
Non-Blocking Concurrency Control (NBCC), introduced in Hudi 1.0, goes further by allowing multiple writers — including concurrent streaming ingestion and table services — to write to the same file group without external locks and without eagerly aborting on conflict, using event-time ordering and file-slice-level reconciliation to merge concurrent changes safely instead.
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