Backend Concurrency and Optimization Questions

Focuses on deep backend system performance and concurrency patterns. Topics include multithreading and synchronization primitives such as locks, mutexes, semaphores, and condition variables; non blocking and lock free data structures; thread pool design and tuning; and approaches for preventing race conditions, deadlocks, and priority inversion. Performance engineering topics include profiling and bottleneck identification, understanding CPU versus memory versus input output bound workloads, cache line behavior and false sharing, non uniform memory access considerations, memory management and garbage collection implications, and techniques for improving throughput and latency. Also covers concurrency models such as event driven architectures, async and await semantics, coroutines, and when to choose message passing versus shared memory. At senior and staff levels, candidates should reason about trade offs between complexity and performance gains, maintainability, observability, and when low level optimization is appropriate versus higher level architectural changes.