TL;DR
Apache Spark 4.1 introduces Real-Time Mode for Structured Streaming, delivering millisecond latency competitive with Flink through concurrent stage scheduling and in-memory shuffle.
Key Points
- Spark 4.1 released December 16, 2025, with Real-Time Mode targeting millisecond latency vs. second-tier latency of original micro-batch approach
- RTM uses concurrent stage scheduling instead of sequential execution, eliminating wait time between upstream stages
- In-memory streaming shuffle replaces disk-based shuffle for faster inter-stage data exchange
- Requires only minor code change: switching trigger to RealTimeTrigger for existing Spark Structured Streaming applications
Why It Matters
Organizations heavily invested in Spark can now achieve Flink-competitive latency without migrating to a separate streaming framework or managing additional infrastructure. This significantly reduces operational overhead for teams standardized on Spark while expanding use cases previously requiring Flink.
Source: moderndata101.substack.com