Combine streams, integrate reactive Java code with external systems, and tune performance without hiding blocking or overload problems.
Advanced reactive work is mostly about boundaries. Once multiple streams, schedulers, databases, and brokers are involved, the hard part is no longer syntax. It is preserving ordering, backpressure, cancellation, and failure semantics across subsystem edges.
Use this section to compare stream-composition patterns, external-system integration choices, and optimization tactics that improve throughput without making the pipeline harder to debug.