--- title: "Backend developer interview questions | Orbit" description: "What backend developer interviews usually test, the usual stages, and 17 practice questions with what a good answer covers. Practise free in the warm-up." canonical: https://orbitanswer.com/roles/backend-developer last_reviewed: 2026-10-18 --- [Companies](https://orbitanswer.com/companies) [Roles](https://orbitanswer.com/roles) [Free warm-up](https://orbitanswer.com/warmup) - [Home](https://orbitanswer.com/) - [Roles](https://orbitanswer.com/roles) - Backend developer Role interview guide # Backend developer interview questions and what to expect Backend developer interviews usually focus on APIs, databases and how a service behaves under load or failure, alongside coding in the role's main language (often Java, Python, Node.js, Go or C#). Candidates commonly report questions on SQL and indexing, caching, concurrency and authentication, and for experienced roles, a system design round and stories about production incidents. What candidates commonly report; it varies by employer, level and country. Last reviewed 18 October 2026. [Practise a backend developer mock interview](https://orbitanswer.com/register) [Warm up free on these questions](https://orbitanswer.com/warmup?track=role%3Abackend-developer) ## The usual stages - 1 Recruiter or HR screen - 2 Online coding test or take-home: often a coding problem or a small API to build - 3 Coding interview in the role's main language - 4 Backend fundamentals: databases, APIs, caching, concurrency and your framework - 5 System design for experienced roles: design a service and discuss scale and failure - 6 Hiring manager or behavioural round ## What interviewers check - Clean API design: resources, status codes, versioning and errors - Database judgement: schema design, indexes, transactions and query cost - Knowing what happens under load: caching, queues, timeouts and retries - Security basics: authentication, authorisation and validating input - Debugging from logs and metrics, and owning production issues - Real depth in one language and framework ## Behavioral questions ### Tell me about a production incident you were part of. What was your role in fixing it? A good answer covers - What users saw and how the team found out - What you checked and how you narrowed down the cause - The fix and the follow-up: alerts, tests or design changes ### Describe a time you sped up a slow API or query. How did you find the problem? A good answer covers - How slow it was and who it affected - How you found the cause: query plans, profiling, tracing - What you changed, with before-and-after numbers ### Tell me about a time you had to change a database schema or API that other teams depended on. A good answer covers - Why the change was needed - How you kept things working during the change: versioning, backward compatibility, migrating in steps - How you told the other teams, and what you'd do differently ### Tell me about a technical shortcut you took to meet a deadline. Did you go back and fix it? A good answer covers - The shortcut and why it seemed worth it at the time - What it cost later, honestly - How you paid it back, or how you'd decide differently now ## Questions about the job ### What makes a REST API well designed? Talk me through one you've built. A good answer covers - Clear resource names, the right HTTP methods and status codes - Consistent error responses, pagination and versioning - Authentication, rate limits and documentation ### Explain database indexes. How do they speed up reads, and what do they cost? A good answer covers - An index as a sorted structure (often a B-tree) that avoids scanning every row - Composite indexes and why column order matters - The cost on writes and storage, and checking a query plan to confirm an index is used ### What are transactions and ACID, and when might you accept a weaker isolation level? A good answer covers - Atomicity, consistency, isolation and durability in plain words - Problems isolation prevents, such as dirty reads and lost updates - The trade-off between strict isolation and throughput, with an example ### When would you choose a relational database, and when a NoSQL store? A good answer covers - Relational for structured data, joins and strong consistency - Document, key-value or wide-column stores for flexible shapes or very high write rates - Letting the access patterns decide, with an example from your work ### How would you add caching to a read-heavy service, and how do you stop it serving stale data? A good answer covers - What to cache and where: in memory, a shared cache such as Redis, a CDN - Expiry times, clearing entries on writes, and cache-aside versus write-through - What happens if the cache goes down or many requests miss at once ### Explain the difference between authentication and authorisation, and how token-based login works. A good answer covers - Who you are versus what you're allowed to do - Issuing a signed token, sending it with each request and verifying it on the server - Expiry and refresh tokens, and storing passwords with a slow, salted hash ### Your service calls a payment provider that sometimes times out. How do you make this safe? A good answer covers - Timeouts, and retries with backoff rather than retrying blindly - Idempotency keys so a retry can't charge the customer twice - Recording each payment's state and reconciling uncertain ones later ### Talk me through how you'd design a notification service that sends email, SMS and push messages. A good answer covers - Requirements: volume, priority, user preferences and quiet hours - A queue between the API and the senders, with retries and a dead-letter queue - Rate limits per provider, avoiding duplicates, and tracking delivery ### Two requests update the same record at the same moment and one change is lost. Why, and how would you prevent it? A good answer covers - The read-modify-write race and why it happens - Fixes: row locks, optimistic locking with a version number, single atomic updates - How you'd reproduce it in a test ### When would you put a message queue between two services instead of a direct API call? A good answer covers - Moving slow or unreliable work out of the user's request - Absorbing spikes and retrying failures - The costs: delayed consistency, duplicate messages, harder debugging ### Explain how your main framework handles a request, from reaching the server to sending the response. A good answer covers - Routing, middleware, the handler and the response - Where validation, authentication and error handling sit - How it serves many requests at once: threads, an event loop or worker processes ## Motivation and fit ### Why backend development rather than frontend or full-stack work? A good answer covers - What you enjoy: data, reliability, scale, the logic behind the product - An example from your work or projects that shows it - What you'd like to learn next ### What would you want to know about our systems and team before your first week? A good answer covers - Questions about the stack, on-call, and how code is reviewed and shipped - A question that shows you've looked at the product - What a good first three months looks like to them ## Tips - Know your main language deeply: its concurrency model, how memory is managed, and the usual libraries for web work. - In any design question, ask about traffic, data size and how stale data is allowed to be before drawing boxes. - Bring up failure without being asked: timeouts, retries, duplicates and what happens when a dependency is down. - Practise reading a query plan and explaining why an index is or isn't being used. - Have one incident story ready with a timeline, your part in it and what changed afterwards. ## Practise it out loud A mock interview asks what backend developer interviews usually test, follows up on your answers and gives you a report. The warm-up is free, needs no account and checks five of these questions as you answer. [Practise a backend developer mock interview](https://orbitanswer.com/register) [Warm up free on these questions](https://orbitanswer.com/warmup?track=role%3Abackend-developer) ## About this guide Written by Orbit from what candidates and interviewers commonly describe for this kind of job. The questions are Orbit's own practice questions, not questions taken from any employer's interviews. Processes change, so check the job post and what your recruiter tells you. ## Company guides to read with this one - [BrowserStack BrowserStack runs a cloud testing platform that lets teams test websites and apps on real browsers and devices, and it describes itself as remote-first. 14 practice questions](https://orbitanswer.com/companies/browserstack) - [Adobe Adobe's careers site describes a call with a Talent Partner, an interview with the hiring manager, then skills assessments and team interviews: coding… 14 practice questions](https://orbitanswer.com/companies/adobe) - [Accenture For freshers in India, candidates commonly report online cognitive, technical and coding assessments and a spoken-English communication test, followed by one… 14 practice questions](https://orbitanswer.com/companies/accenture) - [CRED Candidates commonly report that CRED's engineering interviews include problem-solving and machine coding or design rounds, followed by conversations about how… 13 practice questions](https://orbitanswer.com/companies/cred) ## More guides: software engineering - [Cybersecurity analyst Cybersecurity analyst interviews usually test networking and operating-system basics, common attacks, and how you'd respond to an alert or incident. 17 practice questions](https://orbitanswer.com/roles/cybersecurity-analyst) - [DevOps engineer DevOps and site reliability interviews usually cover Linux, networking, CI/CD, containers and at least one cloud platform, and lean heavily on… 18 practice questions](https://orbitanswer.com/roles/devops-engineer) - [Embedded engineer Embedded engineer interviews usually go deep on C, microcontroller basics and how software meets hardware: interrupts, memory, timing and communication… 17 practice questions](https://orbitanswer.com/roles/embedded-engineer) - [Frontend developer Frontend developer interviews usually test JavaScript, HTML and CSS fundamentals, then a framework such as React, often through a live exercise building or… 17 practice questions](https://orbitanswer.com/roles/frontend-developer) - [Full-stack developer Full-stack developer interviews usually check that you can build a feature end to end: a working interface, the API behind it and the database underneath. 17 practice questions](https://orbitanswer.com/roles/full-stack-developer) - [Mobile developer Mobile developer interviews usually go deep on one platform (Android with Kotlin, iOS with Swift, or a cross-platform framework such as Flutter or React… 17 practice questions](https://orbitanswer.com/roles/mobile-developer) [All 32 role guides](https://orbitanswer.com/roles) [Guides by company](https://orbitanswer.com/companies)