Systems

9 posts in this domain.

• Why circuit breakers exist Backoff makes a single retry polite. But when a downstream is plainly down, every caller in your fleet generously retrying it is the actual problem. A circuit breaker is the small piece that says: stop calling for a while — the answer isn't going to change in the next 50 ms. Apr 29, 2026 · intro
• Why memory-mapped files exist Why hand a file to the OS as memory instead of reading it byte by byte? Because the OS was already caching it that way — and pretending otherwise costs you a copy you don't need. Apr 29, 2026 · intermediate
• Why monotonic time is different from wall-clock time Wall-clock time tells you what to put on a calendar. Monotonic time tells you how long something took. Confusing them is how you get bugs that look like physics violations. Apr 29, 2026 · intermediate
• Why Linux has an OOM killer Linux promises memory it doesn't have, then has to break the promise — the OOM killer is the reaper that decides who dies so the system can keep running. Apr 29, 2026 · intermediate
• Why virtual memory exists Every process thinks it owns the whole machine. That lie is the foundation almost every modern OS feature is built on. Apr 29, 2026 · intermediate
• Why containers won over VMs Both promise isolated, reproducible environments. One boots in milliseconds and ships in megabytes; the other boots in seconds and ships in gigabytes. The reason isn't 'containers are lighter VMs' — they're a different kind of thing entirely. Apr 29, 2026 · intermediate
• Why fork() is such a weird API Other systems take a program and arguments. Unix takes your whole process and clones it. The reasons are half historical accident, half deep insight — and the seams still show. Apr 29, 2026 · intermediate
• Why syscalls are expensive A function call costs a few cycles. A system call costs hundreds — sometimes thousands. The gap isn't sloppy engineering; it's the price of the user/kernel boundary. Apr 29, 2026 · intermediate
• Why idempotency keys exist The network can drop your response after the work is done. Now you have to retry — and you have no idea whether you'd be doing it for the first time or the second. Idempotency keys are the small protocol the client and server agree on so the retry is safe. Apr 29, 2026 · intro