Interview questions with answer breakdowns — Page 46 of 52
Browse page 46 of Offer.cc interview question and answer breakdowns with reasoning, implementation details, follow-ups, and public sources.
How Would You Define Success Metrics for a New Product Feature?
Start from user value, define one primary metric plus diagnostic and guardrail metrics, and use auditable definitions and experiment rules so feature usage is not mistaken for impact.
Operating Systems Interview: What Is a File Descriptor, and How Do You Debug Too Many Open Files?
A production-focused explanation of Linux FD tables, open file descriptions, EMFILE versus ENFILE, /proc diagnostics, leak detection, capacity planning, and fix verification.
How would you implement a stable bounded priority queue?
Use binary heaps to build a fixed-capacity priority queue with FIFO tie-breaking, admission, eviction, and clear complexity trade-offs.
System Design Interview: Design a Service Discovery System
Design registration, health decisions, and endpoint propagation for dynamic multi-region services, with emphasis on control/data-plane separation, staleness bounds, rolling deployments, and failure verification.
Backend Interview: How Do You Design an API for Long-Running Operations?
Start with HTTP 202, an operation resource, and an explicit state machine to design a long-running API with idempotent submission, controlled polling, cancellation, durable errors, result retention, and failure recovery.
Data Engineering Interview: How Do You Choose a Partitioning Strategy and Prove Partition Pruning Works?
Derive an analytics-table partition strategy from query predicates, data volume, skew, and maintenance needs, then verify pruning with plans, scan bytes, and correctness checks.
Networking Interview: How Does the TLS 1.3 Handshake Work, and When Is 0-RTT Safe?
Explain the full handshake, certificate authentication, HKDF key schedule, session resumption, and the HTTP replay boundary that determines whether 0-RTT is safe.
Coding Interview: How Would You Build a Dependency-Aware Task Scheduler?
Implement a dependency-aware scheduler with ready nodes, failure propagation, cycle diagnostics, concurrency limits, and cancellation semantics.
System Design Interview: How Would You Design a Search Autocomplete Service?
Design a low-latency search autocomplete service by deriving capacity, separating offline ranking from online lookup, and making index publication, moderation, and failure recovery explicit.
Backend Interview: How Do You Keep a Database and Cache Consistent?
Start with cache-aside invalidation, then handle lost invalidations, late stale fills, and replica lag with a bounded-staleness budget, a transactional outbox, and version fences that can be tested under failure.
SQL Interview: Calculate an Ordered Conversion Funnel Within 24 Hours
Solve a PostgreSQL ordered-funnel interview question with a precise cohort anchor, stepwise event matching, a 24-hour window, deterministic tie-breaking, rate calculation, and adversarial tests.
TCP Connection Lifecycle: Handshake, Teardown, and TIME_WAIT
Explain TCP establishment and teardown through sequence synchronization, socket states, and the active closer, then diagnose TIME_WAIT and connection failures with ephemeral-port capacity, error types, and packet evidence.
Coding interview: Implement a Cuckoo Filter with deletion
Implement approximate membership queries and explain fingerprints, two candidate buckets, bounded kicks, false positives, and resizing.
System Design Interview: Design a Real-Time Payment Fraud Detection Platform
Derive a real-time payment fraud platform from a decision contract, idempotent velocity state, online and offline features, rules plus model scoring, graded actions, delayed labels, replayable audits, and explicit degradation policies.
Backend Interview: How Do You Rotate JWT Signing Keys Without Causing Authentication Outages?
Design a verifiable JWKS rotation protocol that handles caching, unknown kids, issuer outages, and key compromise without rejecting valid old or new tokens.
Data Engineering Interview: How Do You Design a Right-to-Erasure Data Deletion Pipeline?
Design a durable, auditable workflow that finds a subject across live, derived, immutable, and backup data, prevents resurrection, and proves completion.
Operating Systems Interview: How Do Virtual Memory and Page Faults Work?
Use a Linux service that maps a 20 GiB read-only index to explain page tables, TLBs, minor and major faults, RSS and PSS, then diagnose and improve cold-start latency.
Coding Interview: Implement a Hashed Timing Wheel Timer
Manage many approximate timers with a timing wheel while handling cancellation, rotations, long delays, concurrency, and clock precision.
System Design Interview: How Would You Design a Distributed Tracing Platform?
Design a multi-tenant distributed tracing platform from context propagation and span ingestion through trace assembly, sampling, indexing, and failure recovery, with a recomputable capacity model and a deep analysis of tail sampling.
Backend Interview: How Do You Design a Secure File Upload API?
Design a quarantined upload lifecycle that prevents malicious files, unauthorized downloads, scan races, and resource exhaustion.
Data Science Interview: How Do You Design an A/B Test Under Network Interference?
Define the rollout effect you need, map spillover and carryover, then choose cluster, switchback, saturation, or isolated-universe randomization with design-consistent power and analysis.
How Do You Prevent, Detect, and Recover from Deadlocks?
Diagnose deadlock from the four necessary conditions and a wait-for graph, prove why global lock ordering prevents cycles, and define runtime detection, transaction recovery, and deterministic tests.
Coding interview: Validate a UTF-8 byte sequence
Use a remaining-byte counter and bit masks to validate 1–4 byte UTF-8 sequences online, including truncation and illegal continuation bytes.
System Design Interview: How Would You Design a Real-Time Game Leaderboard?
Start from the ranking contract, trusted score ingestion, ordered indexes, and versioned snapshots to design a real-time game leaderboard for 50 million players with exact personal ranks and safe season settlement.