Software engineering interview prep: coding, system design and behavioural rounds

The usual stages

1. Recruiter or phone screen. A short call about your background, why you are interested and practical matters such as location and timing. Have a two-minute summary of your experience ready.
2. Technical screen. Often a coding problem in a shared editor or a take-home exercise. The goal is to check you can actually write working code.
3. Coding interviews. One or more sessions solving problems on data structures and algorithms, sometimes more practical tasks like building a small feature or fixing a bug in an existing codebase.
4. System design. For mid-level and senior roles: designing something like a URL shortener, a chat service or a news feed at a high level.
5. Behavioural interviews. Questions about how you have worked with others, handled conflict, made mistakes and delivered projects.

Preparing for coding rounds

• Cover the core topics: arrays and strings, hash maps, two pointers, sliding windows, stacks and queues, linked lists, trees and graphs (breadth-first and depth-first search), sorting and binary search, recursion, and basic dynamic programming.
• Practise by pattern, not by volume. Solving a few problems of each type and understanding why the approach works is worth more than racing through hundreds.
• Talk while you code. Interviewers assess your thinking, not only the answer. State your approach, its time and space complexity, and the trade-offs before you write code.
• Test your own code. Walk through an example by hand and check edge cases: empty input, one item, duplicates, very large values.
• Do timed mock interviews, ideally with another person. Solving a problem alone in silence is a different skill from solving it while being watched.

Preparing for system design

• Start with requirements: who uses it, what it must do, roughly how much traffic, and what matters most (speed, consistency, cost).
• Sketch the main components: clients, load balancer, application servers, database, cache, message queue, storage.
• Discuss the data model and the main read and write paths.
• Then talk about scaling and failure: what breaks first, and how you would handle it.
• There is no single right answer. Interviewers want to see you reason about trade-offs and adjust when they add a constraint.

Behavioural questions and the STAR method

• Situation: brief context.
• Task: what you were responsible for.
• Action: what you did, specifically. Say "I", not only "we".
• Result: the outcome, ideally measurable, and what you learnt.

Questions to ask them

• What does a typical week look like for someone in this role?
• How is work planned and prioritised in the team?
• How do code review and deployment work?
• What would success look like in the first six months?
• What is the hardest problem the team is working on now?

On the day

• Test your camera, microphone and the coding tool beforehand for remote interviews.
• If you go blank, say so and talk through a simpler version of the problem. Silence hurts more than a slow start.
• Ask clarifying questions before you start coding.

After the interview

• Send a short thank-you note to the recruiter if that is common where you are applying.
• Write down the questions you were asked while you still remember them, and what you would do differently.
• If you are rejected, ask politely for feedback. Not every company gives it, but some do, and it is valuable.
• Treat each interview as practice. Most people do several before they get an offer.