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Backend Engineer Interview Questions
Practice 9403 coding, system design and machine learning questions from 546 companies, sorted by role, topic and interview round. Every question has step-by-step hints, a code runner that supports 8 languages and an AI mentor; members also get the full solution walkthrough.
- 9403
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- 546
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- 11
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Showing 1–25 of 25 results
- AirwallexMediumBackend EngineerAI-Assisted Build: Tic-Tac-Toe Logic Grown Into a Frontend and Backend App
An AI-assisted coding exercise: build a two-player Tic-Tac-Toe game, then grow it into an application with a frontend and a backend while using AI tools. Tests correct game rules, server-side validation, API design, and the ability to understand, debug and verify AI-generated code.
Software Engineering FundamentalsOther - ArmMediumBackend EngineerExplain timing and testability concepts
This question evaluates a candidate's understanding of digital timing and testability concepts—specifically setup and hold timing, clock skew impacts, mitigation of setup/hold violations, and test methodologies such as scan, DFT and MBIST—within backend digital implementation contexts.
Software Engineering FundamentalsOnsite - ByteDanceHardBackend EngineerBackend Fundamentals Deep Dive: MySQL Internals, Redis, and the HTTP/HTTPS Request Lifecycle
This problem tests your depth in database durability mechanisms, caching strategies for consistency, and the network-level steps involved in secure HTTP request handling.
Software Engineering FundamentalsTechnical ScreenMySQLRedisSystem Design - ByteDanceHardBackend EngineerExplain Backend Fundamentals and AI Tooling
This question tests foundational knowledge across systems engineering, database design, version control, and modern AI integration strategies.
Software Engineering FundamentalsHR ScreenSystems DesignDatabasesGit - ChimeMediumBackend EngineerDesign browser history across tabs
This question tests the ability to design an efficient data structure for navigating browser history, requiring careful management of back/forward states across multiple independent tabs.
Software Engineering FundamentalsTechnical ScreenData StructuresStacksHash Maps - CoinbaseMediumBackend EngineerEvolve Cursor Pagination Without Breaking Clients
This problem tests the ability to design stable, deterministic cursor-based pagination systems that handle non-unique sort keys and schema evolution without breaking backward compatibility.
Software Engineering FundamentalsOnsiteAPI DesignPaginationSQL - CrowdstrikeMediumBackend EngineerImplement a Risk-Score Priority DetectionStore With Put and GetNext in C++
Implement a C++ DetectionStore whose Put stores security detections with an id, an unsigned risk score and a payload, and whose GetNext removes and returns the next detection by risk score as a unique_ptr. Tests priority-structure choice, ownership semantics, tie and duplicate-id policies, and thread safety.
Software Engineering FundamentalsTechnical Screen - HarveyMediumBackend EngineerExplain project decisions and trade-offs
This question evaluates proficiency in technical decision-making, trade-off analysis, and system design ownership for backend projects, including architecture rationale, technology selection, and the candidate's specific role and measurable impact.
Software Engineering FundamentalsOnsite - InstacartMediumBackend EngineerDebug Metrics Computed Before Filtering
Debug a metrics endpoint whose summary is calculated before user filters are applied even though its rows are filtered correctly. Trace the data lineage, aggregate over the full matched population before pagination, preserve security scoping, and add unit and endpoint regression tests.
Software Engineering FundamentalsOnline Assessment - LatitudeaiMediumBackend EngineerDesign a Thread-Safe Bounded Blocking Queue
Tests your ability to design a concurrent, thread-safe bounded blocking queue using synchronization primitives, handle edge cases like spurious wakeups and timeouts, and cleanly coordinate shutdown across multiple threads.
Software Engineering FundamentalsOnsiteConcurrencyMultithreadingQueue - LegoraMediumBackend EngineerDesign a Cloud-Agnostic Upload Adapter
Design a provider-neutral object storage upload client that unifies cloud SDK behaviors while supporting streaming, multipart uploads, error normalization, and provider-specific escape hatches.
Software Engineering FundamentalsOnsiteapi-designcloud-storageobject-oriented-design - MintlifyMediumBackend EngineerDesign a CRUD API for a document service
Design the create, read, update and delete API for a document service, covering the resource model, endpoints, request shapes and status codes. It tests REST fundamentals plus production concerns such as concurrent edits, idempotent retries, pagination, authorization, deletion semantics and API versioning.
Software Engineering FundamentalsOnsite - MintlifyMediumBackend EngineerShould you add an index for a slow query on a large table's unindexed columns?
A query on a large database table is slow and the columns it filters on have no index: should you add one? It tests reading query plans, weighing selectivity and query frequency against write cost, designing composite or partial indexes, and building an index safely on a busy production table.
Software Engineering FundamentalsOnsite - NielsenMediumBackend EngineerDesign a Train Ticket Booking System
This problem evaluates your ability to design a robust reservation system that handles concurrent bookings, maintains data integrity, and adheres to clean object-oriented design principles.
Software Engineering FundamentalsTechnical ScreenConcurrencySystem DesignDatabase - OktaMediumBackend EngineerBuild and Review a Configurable Node.js Token-Bucket Rate Limiter
Implement a configurable Node.js Express token-bucket rate limiter with monotonic refill, HTTP 429 responses, code-review reasoning, and multi-instance limits.
Software Engineering FundamentalsOnsite - OktaMediumBackend EngineerRepair an Express Authentication Endpoint Without Blocking the Event Loop
Repair an Express authentication endpoint with input validation, asynchronous bcrypt, safe errors, correct HTTP status codes, and event-loop-aware resource controls.
Software Engineering FundamentalsOnsite - RedditMediumBackend EngineerDesign Tennis Scoring with Pluggable Rules
Design a testable tennis game scoring component with point recording, readable scores, terminal-state handling, and stable player identity. Keep standard Deuce and Advantage rules separate from pluggable alternatives such as no-ad scoring, and discuss audit history and serialization.
Software Engineering FundamentalsTechnical Screen - RipplingMediumBackend EngineerProcess a Task List: Deduplicate, Drop Completed, Sort by Priority, and Nest Subtasks
Senior backend coding question: process a batch of scheduler tasks by removing duplicates on description and due date, dropping completed tasks, sorting by priority, and placing each subtask directly after its parent. It tests clarifying ambiguous policies, orphan and cycle handling, O(n log n) design, and verified use of an AI coding assistant.
Software Engineering FundamentalsOnsite - RokuMediumBackend EngineerExplain concurrency and distributed fundamentals
This question tests fundamental knowledge of thread-safe collections in Java and core distributed systems architectural patterns, specifically partitioning strategies.
Software Engineering FundamentalsOnsiteJavaConcurrencyDistributed Systems - Scale AIEasyBackend EngineerBuild a CSV-to-JSON Classification Service
Implement a resilient data pipeline service that parses CSV records, enriches them using an external classification client with validation and retries, and writes ordered, structured JSON Lines output safely.
Software Engineering FundamentalsOnsiteData PipelinesConcurrencyError Handling - SpotifyMediumBackend EngineerOn-Call Case Study: Debugging a Misbehaving Production Server
A Spotify on-call case study: as the engineer paged about a misbehaving production server, investigate by asking for metrics, logs and command output. It tests triage, impact assessment, systematic host and service diagnostics, mitigation trade-offs and incident follow-through.
Software Engineering FundamentalsOnsite - SpotifyMediumBackend EngineerVisit-Pattern Counter: Multi-Input Runtime Analysis and Production Hardening
A Spotify backend coding follow-up: for a function that finds the three-website visit pattern followed by the most distinct users, analyze time and memory using separate input dimensions such as records, users, longest per-user history and distinct sites. It also asks which functional and style changes the code needs before it ships in production.
Software Engineering FundamentalsOnsite - TargetMediumBackend EngineerImplement a Synchronized First-Available Seat Allocator
This problem tests your ability to design a thread-safe allocator that manages a finite resource pool under high concurrency, focusing on atomic updates and race condition prevention.
Software Engineering FundamentalsOnline AssessmentConcurrencyAtomic OperationsThread Safety - TeslaMediumBackend EngineerExplain reliability and runtime fundamentals
This question evaluates understanding of reliability and runtime fundamentals in backend engineering, covering competencies such as fault tolerance, end-to-end request lifecycles, API gateway degradation, storage engine selection for search, and the distinction between compilers and interpreters.
Software Engineering FundamentalsOnsite - ZipHQMediumBackend EngineerFind Bugs in an LRU Cache
Identify behavioral bugs in a Java-based LRU Cache implementation using LinkedHashMap, write minimal failing tests, and provide the corrected code.
Software Engineering FundamentalsTechnical Screenjavadata-structuresdebugging
Airwallex
Arm
Chime
Coinbase
Crowdstrike
Harvey
Instacart
Mintlify
Nielsen
Okta
Reddit
Rippling
Scale AI
Spotify
Tesla
ZipHQ