Deployment & Operational

If the flag system can't be reached, the app should fall back to a safe default instead of crashing or hanging, usually the last value it knew, cached locally. For most features, safe means off; for a kill switch protecting against a broken dependency, safe might mean staying off (fail closed) so the risky code never runs by accident.

Skip it when the extra server, delay, and upkeep aren't worth it — for example, low-stakes data, a small team that can't run two systems well, or when a simpler tool like a managed API gateway with good input checks already covers the risk.

It makes each user's experience predictable and consistent, since their requests always hit the same copy of the data instead of racing replication delays between regions. The trade-off is that when their home region goes down and they get sent somewhere else, they might briefly see slightly older data until things catch up.

A sidecar works with any programming language and can be upgraded without touching app code, but it costs extra memory/CPU per instance and adds a tiny delay. A library is lighter and faster but only works in one language and needs every app to be rebuilt to upgrade it.

This is cache poisoning: the CDN stored a wrong or attacker-influenced response under a cache key that many different users then hit, so instead of one broken response for one weird request, everyone gets served the bad cached copy.

Low hit ratio usually means too many different edge locations each independently asking the origin for the same file, or the cache expiring too fast. An origin shield adds one extra caching layer between the edges and the origin so only one edge has to fetch a file the first time, and every other edge gets it from the shield instead.

You'd group workloads by resource profile and priority, cap what each can use, watch real usage instead of guesses, and keep critical stuff separated from risky/bursty stuff — then keep adjusting as workloads change.

If the store goes down or serves bad data, every dependent service can be affected at once, so it's a single point of failure for the whole fleet. Mitigations: cache last-known-good config locally, version every change so you can instantly roll back, replicate/harden the store, and gate risky changes with canary rollout. For a small number of services, a fully centralized store can be overkill - simpler options (env vars, files in the deploy pipeline) may suffice.

Targeting rules are usually checked in order, top to bottom, and the first one that matches a user wins, so rule order matters a lot. Doing that check in the browser or app is fast but exposes your rules and upcoming features to anyone who inspects the app; doing it on your server keeps rules private but adds a network step.

How you build the pipe between the front-door server and the real worker matters as much as having two servers at all — a narrow, structured pipe with short-lived, limited permissions keeps a break-in small, while a wide-open one lets it through anyway.

In one region, you flip a switch and everyone's on the new version at once. Across four regions, you roll out gradually, so for a while some regions run old code and some run new - meaning the database has to work for both at the same time, or things break for whichever region hasn't updated yet.

Two separate problems: pods dying before their sidecar finishes forwarding the last requests causes brief errors during deploys, and every pod carrying its own extra proxy process, multiplied by thousands of pods, slowly eats memory across the cluster.

Skip stamping when you're small — running many full stacks for a handful of customers just wastes money and adds complexity you don't need yet. For features needing a global view across all stamps (search, reporting), teams usually copy data out of every stamp into one separate system built just for that.

If content changes per user or per request, is accessed rarely, or must never leave certain servers or regions for legal reasons, caching it broadly on a CDN either doesn't help or actively causes problems, so you'd keep it dynamic or restrict it instead.