Apple SRE / Production Engineer interview questions

Latency fine, loss low, link idle, yet a single copy takes hours. The arithmetic of bandwidth-delay product settles this question before any tool opens.

Guaranteed capacity and discounted capacity are different products. Peak season needs both, arranged in layers and verified with a game day before the traffic arrives.

Generation works when the inputs are genuinely data and dies when YAML grows loops. The line between encoding decisions and writing a worse programming language is where these interviews are actually scored.

The kubelet is a local reconcile loop with its own event stream, probe workers and eviction brain. The detail worth holding onto is that Ready status can reflect either a reported health failure or missing heartbeats, and those have different causes and different fixes.

The registry is often assumed to figure it out. The real mechanism is an index of per-platform manifests and a client-side choice at pull time, and knowing which layer makes that choice is the whole question.

Scale-downers mark a node removable only when every pod on it can leave safely. Your batch workload died because nothing marked it special. The mechanism is a filter cascade, and the fix is priorities, PDBs and annotations.

The app server that proxies uploads through itself is the design that fails this question. Direct-to-storage, validate after arrival, and make CDN invalidation almost never necessary.

Ladders and player logic are the warm-up. Cache topology, egress arithmetic, and knowing which quality metric actually predicts churn are what separate the answers.

Multi-AZ is the answer and the reason matters more than the acronym. Each tier fails differently, and the database is the one where high availability means a failover with a real gap, not zero interruption.

The question that separates people who have debugged a hung rollout from people who have read about one. The interesting half is not the signal, it is PID 1.

One is layer 4 and regional, one is layer 7 and regional, one is layer 7 and global. Answer on those two axes and the choice makes itself, including when you need two of them together.

Ordering and retransmission are what TCP adds, and both of them cost time. Naming something that deliberately gives them up, and saying why, is what turns a textbook answer into a real one.

A deceptively deep question, because there are at least six places a version can get stuck and they span the pipeline, the cluster and the edge. Work the path in order.

A staple of every networking round, and the follow-up is always about TLS termination. Knowing which layer sees what decides most of the answer.

The oldest question in systems interviewing and still the best, because it is unbounded: every layer you can describe is another layer you could debug.

Five stages, and which one you are stuck in tells you what to fix. A machine that reaches a GRUB prompt has a different problem from one that hangs waiting on a filesystem that no longer exists.

The classic ephemeral port exhaustion question. TIME_WAIT is a familiar phrase and the useful facts are narrower: which side accumulates it, and why the popular fix is dangerous.

Compare proxy, hosted and group repositories. Trace a tested artifact into production, and understand when a cache can keep builds running during an upstream outage.

The arithmetic takes thirty seconds to learn and gets asked constantly. What it is really testing is whether you have ever had to size a VPC that could not be resized later.

Most of what looks like used memory on a healthy Linux box is page cache doing its job. Knowing which column to read, and why df and du disagree, is half of Linux triage.

Interviewers use this to sort memorised trivia from people who have chased a slow lookup. Three roles, one bit, and the caching rules most candidates repeat incorrectly.

A growing backlog of sockets waiting for the application to close its side usually points at lifecycle handling. Here is the hunt from ss output to the pool timeout that caused it.

Most hand-written units boot in dev and die in production. The gap is Type selection, restart policy, and the drop-in workflow vendors expect you to respect.

A one-line mistake that locks you out of the obvious fix. The fast recovery teaches more about the permission model than any man page will.