Question bank

4,310 interview questions, answered.

Reference answers, what the interviewer is really testing, how it is graded, and the follow-ups that come next.

Easy 190Medium 2,498Hard 982
FiltersDifficulty, topic, company

4,310 questions

  1. 4225In matched one-hour measurement runs, configuration A costs 12 units/hour and serves 18,000 completed responses, of which 3,000 are late. Configuration B costs 10 units/hour and serves 12,000 timely responses. No other failures occur. Which is cheaper per thousand timely successes, and what does that comparison omit?MediumAI MLSystem design
  2. 4226A shared pool has 12,000 free reserved tokens; tenant T has 4,000 under its active limit. A request needs 6,000 and expires in one second; no release is expected for three seconds. What should admission do, and how should a retry reuse identity?MediumAI MLSystem design
  3. 4227Two replicas each serve30 requests/minute. Arrivals rise to 90. A third replica takes three minutes to become ready; nothing expires or is rejected. Calculate backlog at readiness and whether it drains. What if a fourth is ready then?MediumAI MLSystem design
  4. 4228Four aligned ranks report input waits 20,20,140,20 ms and compute 180 ms each. Their collective completes20 ms after the last rank enters. Should networking be the first change?HardAI MLSystem design
  5. 4229At10:00 a tenant starts long prompts. At10:02 first-token p95 rises0.8→8 seconds, queue p95 reaches6 seconds, and token-gap p95 stays35 ms. No release occurred. Choose an initial mitigation and recovery checks without claiming a proven root cause.HardAI MLSystem design
  6. 4230A consumer calls an external credit API for operation e42. The API applies10 units, but its response is lost before the consumer commits its broker offset. Does broker exactly-once processing prevent a second credit? Design the retry boundary.MediumDataTechnical
  7. 4231Window[12:00,12:10) UTC has values2 at 12:00 and 5 at 12:09. A value 7 at 12:10 belongs to the next interval. An accepted late value 4 occurred12:03. What is the revised first-window sum, how is it published, and what does a watermark not prove?MediumDataTechnical
  8. 4232A three-day replay expects counts100,122,79 after a known parser repair. Candidate output is 101,121,79. The total matches301. Should it replace production, and what must make a second run safe?MediumDataTechnical
  9. 4233A stopped CDC connector retains2 GiB of source log per hour. The source has 8 GiB free and no other disk use in this simplified model. Explain the deadline and the risk of discarding retained logs to free space.MediumDataTechnical
  10. 4234A daily invoice table should contain one row per invoice and required customer references. It has 1,000 rows, a recent timestamp,20 duplicate keys and one missing source partition. Define publication behavior and evidence.MediumDataTechnical
  11. 4235For user a, changes are(v1,upsert,Ada),(v3,delete,null),(v2,upsert,Amy). User b has(v1,upsert,Bo). Versions are unique and authoritative; arrival order is as listed. Write a current-state query and describe safe incremental behavior.HardDataTechnical
  12. 4236A device reports stopped at 09:00, moving at event time09:06 but arriving09:11, and stopped again09:08. The rule requires ten uninterrupted event-time minutes, with the late movement accepted. Give eligibility and delivery identity.HardDataTechnical
  13. 4237A Deployment desires3 replicas;3 Pods exist, only 1 is ready, and clients see failures through its Service. What evidence do you collect before changing replica count?MediumSystem designTechnical
  14. 4238A node has 8 allocatable CPUs and existing ordinary-container requests total 7.2. A pending Pod requests 0.7 for its app and 0.3 for a sidecar. Live CPU is 20%. Assume no init or Pod-level resource effects. Why can it remain Pending?MediumSystem designTechnical
  15. 4239A healthy API process loses its shared database. Cached catalogue reads still work, but writes fail. The current liveness probe checks the database and repeatedly restarts every Pod. What policy would you propose?MediumSystem designTechnical
  16. 4240A destination Pod is selected by two ingress policies: one allows only app=api and another allows all Pods in the namespace. A test Pod in that namespace connects. The network provider enforces policy. Why?MediumSystem designTechnical
  17. 4241A Deployment has 4 replicas, maxUnavailable=0 and maxSurge=1. Nodes have no spare requested capacity for the surge Pod. Old replicas meet demand only while all four serve. Does this prove a zero-downtime rollout?MediumSystem designTechnical
  18. 4242Five comparable developers try to create and deploy a service. Four complete unassisted in20,25,30,35 minutes; one finishes in60 minutes with assistance. What platform outcome do you report and test next?MediumSystem designTechnical
  19. 4243From the same client, PodIP:8080 succeeds. ServiceIP:80 and the Service DNS name on port 80 both fail. DNS resolves to the expected Service IP. The Service selects the ready Pod but targetPort is 9090. Diagnose the layer and next check.HardSystem designTechnical
  20. 4244A team may scale only its approved Deployment from 2 to 8 replicas. A service backend can modify many namespaces. Two requests arrive with the same operation ID but different desired counts. Define authorization and concurrency behavior.HardSystem designTechnical
  21. 4245A red admin reads invoice I1 with private fields. The API caches by invoice ID. A red viewer may see only summary fields and later receives that cache entry. The database query was tenant-scoped. Diagnose and repair.MediumTechnical
  22. 4246A preview endpoint needs three known HTTPS hosts. The first URL is allowed but redirects internally; another allowed response streams without end. Specify controls and local verification.MediumTechnical
  23. 4247A key appears publicly at 09:00, the page is removed09:20, and the key is revoked 09:35. It could create other credentials. Logs begin 09:10. What does 'rotated, closed' omit?MediumTechnical
  24. 4248An OIDC trust rule accepts any token from the CI issuer with environment=production. Another repository can use that environment name, and the resulting role can create administrators. Identify distinct remaining risks.MediumTechnical