Processes vs Threads: How Your Concurrency Choice Shapes Stability and Speed

When writing concurrent code, developers must choose between spawning separate processes or threads within a single process, a decision with significant trade-offs. Processes have isolated memory spaces enforced by the OS, meaning a crash in one process does not affect others — a design browsers use to contain individual tab failures. Threads, by contrast, share a process's memory, making them far cheaper to spawn and enabling fast data sharing without copying, which suits parallelised tasks on multi-core hardware. However, shared memory introduces race conditions, torn writes, and deadlocks when multiple threads access the same data without proper synchronisation using locks. Choosing between the two comes down to whether a workload prioritises fault isolation and safety or low overhead and high-speed data sharing.