IT Interview Questions and Answers: How to Prepare for a Software Job Interview

Top IT interview questions with sample answers

Tell me about yourself.

Keep it to about a minute: your education or current role, your main tech stack, one project or result you are proud of, and why this role fits. For example: "I am a Java developer with two years at a fintech startup, where I built the payment reconciliation service in Spring Boot that now handles 50,000 transactions a day. I am looking for a backend role where I can work on scale."

Explain the four pillars of object-oriented programming.

Encapsulation keeps data and the methods that change it together and hides internal state; abstraction exposes only what a user of the class needs; inheritance lets a class reuse and extend another; polymorphism lets one interface have many implementations, for example method overriding. Give a short example from your own code.

What is the difference between a process and a thread?

A process is a running program with its own memory space; threads are units of execution inside a process that share its memory. Threads are lighter to create and switch, but shared memory needs synchronisation (locks) to avoid race conditions.

How do you find the second highest salary in SQL?

One common answer: SELECT MAX(salary) FROM employee WHERE salary < (SELECT MAX(salary) FROM employee); or use DENSE_RANK() OVER (ORDER BY salary DESC) and pick rank 2, which also handles ties. Mention which one you prefer and why.

What is the difference between SQL and NoSQL databases?

SQL databases store data in tables with a fixed schema and support joins and ACID transactions, good for relational data like orders and payments. NoSQL databases (document, key-value, column, graph) have flexible schemas and scale out easily, good for large, varied or fast-changing data. The choice depends on the access pattern.

Walk me through a project you worked on.

Use a clear structure: the problem, who used it, the architecture, your own part, one hard problem you solved and the result. Be precise about what you built yourself versus what the team built.

Tell me about a bug or production issue you fixed.

Describe the symptom, how you found the cause (logs, metrics, reproducing it), the fix, and what you changed so it would not happen again, such as a test, an alert or a code review rule.

How would you design a URL shortener?

Clarify the scale first (reads vs writes per second). Then: an API to create and resolve links, a unique short key (base62 of an ID or a hash with collision checks), a database for key-to-URL mapping, a cache for popular links, and analytics written asynchronously. Discuss expiry, abuse prevention and scaling reads.

What happens when you type a URL in the browser?

DNS resolves the domain to an IP, the browser opens a TCP connection (and TLS for HTTPS), sends an HTTP request, the server returns a response, and the browser parses HTML, loads CSS, JavaScript and images, and renders the page.

How do you make sure your code is good before it goes live?

Unit and integration tests, a code review by a teammate, static checks or a linter in CI, testing on a staging environment, and monitoring after release so problems are caught early.

Why do you want to leave your current company?

Stay positive and forward-looking: the kind of work, scale or learning you want next, and how this role offers it. Avoid complaints about people or pay alone.

What is your expected CTC?

Give a researched range based on your experience, skills and the role, and say you are open to discussing the full package. If you have a competing offer, you can mention it honestly.