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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
- Questions
- 546
- Companies
- 11
- Topics
- 8
- Languages
Showing 31–60 of 91 results
- 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 - MetaMediumBackend EngineerSolve coding and AI-assisted tasks
This problem tests your ability to manipulate tree structures with parent pointers and verify path validity under specific movement constraints.
Coding & AlgorithmsOnsiteTreesData StructuresAlgorithms - 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 EngineerHiring-manager screen: past work, full-stack flexibility, and why join a startup
A hiring-manager screen for a senior backend role asks you to walk through your previous work, describe your full-stack experience and whether you would take on frontend work, and explain why you want to join a startup and this company. It tests concise storytelling, flexibility and genuine motivation.
Behavioral & LeadershipOnsite - 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 - New RelicMediumBackend EngineerCompress a String by Run-Length Counts, Keeping the Original When Not Shorter
Implement run-length string compression that replaces each run of repeated characters with the character and its count, returning the original string when the compressed form is not strictly shorter. Tests careful run handling, multi-digit counts, the tie rule, and complexity and edge-case discussion.
Coding & AlgorithmsOnsite - New RelicMediumBackend EngineerDesign a Kafka Consumer Service That Groups Trace Events by Trace ID
Design a distributed service that consumes trace events from Kafka, groups every event sharing a trace ID, and hands each complete trace to an existing processing function. Covers partitioning, in-memory versus external state, deciding when a trace is complete, and traces that stay open for hours.
System DesignOnsite - New RelicMediumBackend EngineerLongest Strictly Increasing Path in a Grid with Four-Directional Moves
Given an integer matrix, find the number of cells on the longest path whose values strictly increase, moving only up, down, left, or right with no diagonal steps and no wrap-around at the edges. Tests grid search and the ability to turn a working first solution into an efficient one.
Coding & AlgorithmsOnsite - 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 - NuroHardBackend EngineerDesign Webhooks and Metric Aggregation
Design a webhook delivery platform and vehicle telemetry aggregation system. The solution covers multi-tenant subscriptions, at-least-once delivery, retries, signing, DLQs, endpoint isolation, high-volume ingestion, stream processing, raw storage, rollups, alerting, late events, and downsampling.
System DesignOnsite - NuroHardBackend EngineerImplement BFS and a Job Scheduler
Solve grid reveal with BFS and design a thread-safe periodic job scheduler. The solution covers Minesweeper-style expansion, queue processing, priority-queue scheduling, locks, worker pools, cancellation, duplicate prevention, long-running tasks, clock drift, and backpressure.
Coding & AlgorithmsOnsite - 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 EngineerDesign Cross-Domain SSO and OIDC Access to Third-Party Tools
Design cross-domain SSO with OIDC authorization-code flow, separate site sessions, secure account linking, third-party federation, and delegated API authorization.
System DesignOnsite - OktaMediumBackend EngineerDesign Single Sign-On Across Two Acquired Sites With OIDC Federation
Design cross-domain single sign-on after one company acquires a second site on a different domain, then extend it to many sites and to delegated API access for third-party tools, covering the authorization-code flow, session separation, and the authentication-versus-authorization distinction.
System DesignOnsitesystem-designauthenticationoidc - 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 - OpenAIMediumBackend EngineerConvert IPv4 Ranges to CIDR Blocks
This question evaluates understanding of IPv4 addressing, binary/bitwise manipulation, and the ability to summarize consecutive address ranges into minimal CIDR blocks, and belongs to the Coding & Algorithms domain for backend engineering roles.
Coding & AlgorithmsTechnical Screen - OpendoorMediumBackend EngineerDesign Map-Based Home Search
This problem tests the ability to design a geo-spatial search service capable of handling high-frequency map interactions, filtering, and data consistency at scale.
System DesignTechnical ScreenGeo-spatialCachingScaling - OpendoorHardBackend EngineerExecute a TTL Key-Value Store with Transactions
This problem tests the implementation of an in-memory key-value store supporting TTL expiration, atomic transactions with rollback capabilities, and logical time-based validation.
Coding & AlgorithmsTechnical ScreenHashMapsTransactionsTTL - OracleMediumBackend EngineerAdd One to an Integer Stored as Digits Without ArrayList
This problem tests array manipulation skills and the ability to handle carry-over logic in fixed-size numerical representations.
Coding & AlgorithmsOnsiteArraysMathAlgorithms - OracleMediumBackend EngineerDesign a Distributed Rate Limiter
This problem tests the ability to design a scalable, low-latency distributed system for enforcing traffic quotas across multiple geographic regions with considerations for consistency and burst handling.
System DesignOnsiteDistributed SystemsRate LimitingScalability - OracleMediumBackend EngineerDesign a High-Volume Healthcare Data Ingestion Pipeline
This question tests the ability to design a resilient, high-throughput ETL pipeline for sensitive and messy healthcare data, focusing on fault isolation, data integrity, and architectural scalability.
System DesignOnsiteETLData PipelineScalability - OracleMediumBackend EngineerExplain How You Use AI in Software Engineering
This question assesses the candidate's practical experience with AI-assisted coding tools, their ability to critically evaluate machine-generated output, and their awareness of engineering rigor regarding security and code quality.
Behavioral & LeadershipOnsiteSoftware EngineeringGenerative AICode Review - OracleMediumBackend EngineerExplain a Difficult Technical Decision
This question assesses a candidate's ability to articulate complex technical trade-offs, stakeholder management, and the ability to reflect on past decision-making processes.
Behavioral & LeadershipOnsiteBehavioralArchitectureDecision Making - OracleMediumBackend EngineerFind the Best Profit from One Stock Trade
Tests array traversal, greedy state tracking, and achieving optimal O(n) time and O(1) space complexity for trade optimization.
Coding & AlgorithmsOnsiteArrayDynamic ProgrammingGreedy - OracleMediumBackend EngineerHandle a Tight Deadline You Could Not Meet
This question assesses the candidate's ability to identify project risks early, manage stakeholder expectations through transparent communication, and implement process improvements to prevent recurrence.
Behavioral & LeadershipOnsiteBehavioralLeadershipProject Management - OracleMediumBackend EngineerReturn the K Most Frequent Values with a Larger-Value Tie-Break
This problem tests proficiency with hash maps for frequency counting and custom sorting logic using priority queues or sorting algorithms.
Coding & AlgorithmsOnsiteHash MapSortingPriority Queue - OracleMediumBackend EngineerSplit a String into Exactly Three Palindromes
Tests string partitioning, palindrome verification, and algorithmic optimization using dynamic programming or two pointers.
Coding & AlgorithmsOnsiteStringDynamic ProgrammingTwo Pointers - OtherMediumBackend EngineerCompare Strings With Deletions
This question evaluates string processing and algorithmic optimization skills, specifically handling simulated deletions (backspace behavior) and performing comparisons under a strict auxiliary space constraint.
Coding & AlgorithmsTechnical Screen - 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
Meta
Mintlify
Nielsen
Nuro
Okta
OpenAI
Oracle
Reddit