Meta SRE / Production Engineer interview questions

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.

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: the interviewer stops you when you run out of depth, and where you stop is the score.

The question that reveals whether someone knows what load average actually counts on Linux. It is not a CPU metric, and that single fact resolves the whole thing.

The scripting round in disguise. The constraint is the question: it exists to see whether you stream or whether you load, and everything else is about whether the script is safe to run twice.

The two-syscall duet behind every process on the box. The follow-ups live in what survives the transition, and candidates who skip that fail the next question.

SIGKILL writes no stack trace and the application cannot defend itself. The verdict is already sitting in the kernel ring buffer, and reading it precisely is the skill being priced.

tcpdump copies packets to userland; eBPF aggregates inside the kernel next to the event. Know which hook runs where, what a verifier log is telling you, and when XDP drops for free.

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 single most common Kubernetes interview question, and the one where a vague answer is most obvious. Every stage you name is a place the interviewer can ask you to debug.

Asked in nearly every senior Kubernetes loop, and most candidates answer with a feature list. The scoring answer names the three problems it solves and then argues for not adopting it.

The question that finds out whether you know Kubernetes networking or just use it. The model has three rules and everything about CNI follows from them.

Cilium became the default CNI on major managed platforms for a reason that is mechanical rather than fashionable. The iptables datapath degrades with service count, and eBPF replaces a linear scan with a map lookup.

A registry stores repositories, which hold manifests, which point at content-addressed blobs. Candidates who can draw that hierarchy and the auth dance around it understand every pull failure they will ever meet.

It sounds like trivia and screens for something real: whether you understand that a pod is a shared namespace boundary with an owner, not just a group of containers.

Pod-level SIGTERM handling and node-level shutdown coordination are different mechanisms, and conflating them is the trap. The kubelet can only drain pods on power-off if it participates in systemd's shutdown sequence.

Driver, container toolkit, device plugin, DCGM and discovery must version-match on every node. The operator reconciles that ladder from one ClusterPolicy CR; MIG, upgrades and host kernels are where it bites.

A question where both answers are defensible and the reasoning is the entire score. The operational consequences are concrete: what happens when a shared library needs a security patch.

Long-lived branches pile up merge debt until integration becomes a gamble. There is a named technique that ships a three-month refactor in releasable increments, and its final step is deletion.

The honest mechanics of merging to trunk many times a day: flags, fast CI, trunk locks, and the conditions under which you should not run it at all.

Quarantine is a holding cell with an expiry date, not a landfill. Per-test flake rates, entry evidence, an enforced expiry review, and the cap that turns fixing into priority.

Green PRs can still break main because they were validated against a stale tip. Merge queues revalidate the exact combination that lands, trading latency for certainty.

Build graphs identify affected targets only when their dependencies are complete. The ladder from build-everything to content-addressed caching, hermeticity audits, and where undeclared inputs rot correctness.

Ownership files decay faster than org charts. What separates working CODEOWNERS from rubber-stamp theatre is hygiene: team aliases, stale-owner linting, and keeping review routing apart from paging.

Most candidates discuss caches as a speed feature. The staff-level answer treats write access to a shared cache like deploy credentials and proves hermeticity with sampled cold rebuilds.

The kernel watches syscalls, sockets and short-lived processes that userspace agents polling every few seconds never meet. Know what eBPF adds, what it costs, and the security conversation it starts.

Tests whether you know that Kubernetes waits, and for how long. The default timings surprise most candidates, and they explain why a node failure hurts longer than people expect.

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.

Both can be right, which is the whole point. Retransmissions mean a segment was not acknowledged, and the network is only one of the places that can happen.

Self-healing unavailability is a timeout arithmetic story. Pull the balancer's removal timestamps, lay them against the GC log, and the pause that ejects the instance will be sitting there in plain sight.

The Google-style NALSD round in miniature. The boxes are easy; what is being scored is whether the numbers fall out of Little's law before you draw them.

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.

Dual-writing from application code is the answer that fails quietly six months in. Change data capture, per-entity ordering, and a reindex you could run on a Tuesday are what interviewers score.

Drawing an agent that polls a server is the easy third. The interview is about partial applies, fleet-versus-world state, and why rollback must be a pointer flip, never a reverse edit.

The question that separates people running GPU clusters from people running Kubernetes clusters that happen to have GPUs. The answer is that an integer count cannot express what a GPU workload needs.

The default scheduler places pods one at a time, which is exactly wrong for a job that needs all sixteen or none. Two half-placed jobs can hold each other's GPUs forever without either ever starting.

GPUs fail gradually before they fail loudly. Xid errors, ECC retirement, thermal throttling and a degraded NVLink all produce a node that is up, schedulable, and slowing every gang it joins.

Hard quotas strand idle GPUs and soft quotas mean the loudest team owns the cluster. Borrowing with reclaim is the shape that works, and the interesting decisions are all about what happens when the lender comes back.

At sixteen GPUs and above, the network is the computer. Collectives run at the speed of the worst link in the group, and placement decides which link that is.

A mixed fleet is the normal state, not a transitional one, because capacity arrives when it arrives. The failure is a scheduler that treats two very different cards as the same countable unit.

The fastest-growing design round in infrastructure hiring. GPU economics break the assumptions CPU autoscaling is built on, and the answer has to start from that rather than from Kubernetes.

Requests-per-second is not the load unit, cold starts are minutes not seconds, and scale-in can kill paying users mid-sentence. Everything you know about HPA needs re-deriving here.

Code rollouts ask 'does it work'; model rollouts ask 'is it better', and the second question has no HTTP status code. Shadow traffic, offline eval gates and quality canaries replace the 500-rate dashboards you cannot use.

Both configurations fit the weights. Compare cache capacity, collective overhead and replica placement under the actual traffic shape; neither layout wins every workload.

Prefill and decode are two different workloads sharing one GPU. Their resource demands differ, and an unchunked long prefill can delay active decodes. Profile the actual model and batch shape before choosing a scheduling change.

It trades compute for latency, so it wins on an underloaded fleet and can lose on a saturated one. The acceptance rate decides everything, and the acceptance rate depends on traffic you do not control.

The utilisation number everyone quotes means at least one kernel was resident, not that the hardware was doing useful work. A GPU at 95 percent can be doing five percent of what it is capable of.

A training job is an hours-long computation with no user watching. Whether an interruption costs four minutes or four days is decided entirely by checkpoint cadence and restart semantics designed before the run.

Checkpoint too rarely and a failure costs hours of GPU time. Checkpoint too often and you pay for stalled GPUs writing terabytes to storage. There is an arithmetic answer and most teams never do it.

Code and data are the two things people pin, and they are rarely the two things that changed. The driver, the framework build, the kernel selection and the data ordering all vary underneath a pinned repository.

Failure stops being an event and becomes a rate. Once mean time between failures drops below the length of a run, the design question is not how to avoid interruption but how cheaply you can absorb one.

Expensive accelerators waiting on cheap storage is the most common form of waste in a training cluster, and it looks exactly like a code problem on every dashboard.

The defensiveness test. Interviewers score whether you can extract the one true behavioral signal from stinging delivery, change something observable, and close the loop with the person who said it.

The classic ephemeral port exhaustion question. Most candidates know the phrase TIME_WAIT; far fewer know which side accumulates it and why the popular fix is dangerous.

Two different resources produce the same errno, and the second one is invisible unless you know to look. One command distinguishes them.

A beginner question with a senior follow-up hiding in it. Once you know a hard link is a second name for an inode, log rotation and backup behaviour both stop being mysterious.

Everyone recites the four letters. The scoring answer walks each packet across the wire and knows the places the exchange silently dies.

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 routine cloud operation with three layers that can quietly disagree. The strong answer is an ordered procedure you could run during business hours, without a reboot.

The answer is yes, and then the real question starts. Asymmetric routing and silent drops punish anyone who treats the routing tables as one flat list.

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.