Software Engineer Interview Questions and Answers (2026)

Every question below opens to a full page: a quick answer you could give under pressure, what the interviewer is really probing, how to structure your response, a first-person example answer, and the follow-ups that usually come next. Work through your weakest category first.

Prefer one long read? The full software engineer interview guide covers preparation, process and salary talk in a single article.

Algorithms

Walk me through how you would analyze the time and space complexity o...Answer + example

Data Structures

When would you choose a hash map over a balanced binary search tree?Answer + example

Databases

Explain what ACID means and what each property actually guarantees.Answer + example How does a database index work, and when does adding one make things...Answer + example How do you decide between a relational database and a document store...Answer + example

APIS

When would you use gRPC instead of a REST API?Answer + example What does it mean for an endpoint to be idempotent, and how would you...Answer + example

Systems

Explain the difference between a process and a thread.Answer + example How do you decide what to cache, and how do you handle invalidation?Answer + example

Concurrency

What causes a race condition, and how do you find one that only shows...Answer + example What causes a deadlock, and how would you prevent one?Answer + example

Distributed Systems

Explain the CAP theorem and how it applied to a system you have worke...Answer + example

Runtime

How does garbage collection work, and when does it become a problem?Answer + example

Design

What is dependency injection and what problem does it actually solve?Answer + example

Networking

Walk me through everything that happens when a client sends an HTTPS...Answer + example

Scenario

A service that was fine yesterday now has p99 latency of four seconds...Answer + example Your API is read heavy and the database is sitting at ninety percent...Answer + example How would you design a rate limiter for a public API?Answer + example A third party API you depend on starts timing out intermittently. Wha...Answer + example You need to add a non nullable column to a table with 500 million row...Answer + example You inherit a service with no tests and you need to change its core l...Answer + example

Tooling

When do you rebase and when do you merge?Answer + example

Process

What does a good CI pipeline look like for a backend service?Answer + example How do you decide what to cover with unit tests versus integration te...Answer + example

Observability

What is the difference between logs, metrics and traces, and when do...Answer + example

These are the classics. Your software engineer posting has its own. Paste your actual job description into the free Question Predictor and get the 20 questions that role is most likely to ask, with what each one is really probing.

Predict my questions

Walking into this interview soon? GhostPilot listens to your live call, spots the question the moment it is asked, and puts a structured answer on your screen in real time. Try it on your next mock, or grab a $29 Session Pass, no subscription, for the real thing.

See how it works