A mock interview is a practice interview: someone plays the interviewer, you play the candidate, and you run the round as if it were real. It's the closest thing to interview experience you can get without the stakes, and it's the best way to find out what you'll do under pressure before it matters.
But mock interviews are easy to waste. A friendly chat with a friend who nods along feels like practice and teaches very little. This guide covers how a mock interview works, how to set one up so it's realistic, how to get feedback you can use, and how to fit mocks into your preparation.
Why mock interviews help
Most interview preparation is reading and solo practice: learning patterns, reviewing building blocks, writing out stories. That's necessary, but interviews test something else as well: thinking, explaining, and adapting in real time, with someone else steering. Mock interviews are where you practise that part.
They're especially good at revealing things you can't see alone:
- Timing. How long your answers actually take, and where the time goes.
- Clarity. Whether an explanation that made sense in your head makes sense to a listener.
- Follow-ups. Where your stories, designs, and answers are thin once someone starts asking "why?".
- Habits under pressure. Going quiet, rushing into code, over-explaining the background.
Set it up like the real thing
The more realistic the conditions, the more the mock tells you.
- Pick a specific round. "A mock interview" is too broad. "A 45-minute system design round for a senior backend role" is something you can prepare for and someone can run.
- Use a real time limit, and stop when it ends.
- Use the real format. Video call, shared editor or whiteboard, camera on, the same as you expect on the day.
- Base it on a real job. Give the interviewer the job description, so the questions match the level and the domain. Our guide to preparing from the job description covers turning a posting into prompts.
- No pausing. If you get stuck, work through it the way you would in the interview. That's the practice.
Choosing the interviewer
Who plays the interviewer matters a lot.
- Someone who has interviewed for real is best. They know what interviewers listen for and what good looks like at each level.
- A peer preparing for the same kind of role is a good second choice. Take turns: being the interviewer teaches you a surprising amount about what makes an answer easy or hard to follow.
- A friend outside the industry can still help with the recruiter screen and behavioural rounds. They'll notice rambling and jargon, even if they can't judge the technical content.
Whoever it is, brief them. Give them the round, the job description, the time limit, and a few follow-up questions to use. Ask them to interrupt and push back, because that's what real interviewers do. A mock interviewer who's too polite isn't doing you a favour.
What the interviewer should do
If you're running a mock for someone else, a few habits make it useful:
- Stay in role for the whole session. Don't break off to coach mid-round.
- Ask follow-ups. "What did you do, specifically?" "Why that database?" "What happens if traffic grows ten times?" The follow-ups are where the real learning is.
- Change something. In a design round, change a requirement halfway through. In a behavioural round, ask what they'd do differently.
- Take notes with timestamps, so feedback can point to specific moments.
Feedback that's useful
Right after the session, spend ten to fifteen minutes on feedback. Generic feedback ("that was good", "be more confident") doesn't help. Useful feedback is specific, points to moments, and suggests something to try:
- What went well. Specific moments to keep doing. "Writing the requirements down first meant you referred back to them three times."
- Focus areas. Two or three things to work on, not ten. "You spent eight minutes on the situation in your first story, which left little time for what you did."
- Something to try next time. "Next time, open with the decision you made and fill in context only if asked."
As the candidate, write the feedback down before you forget it, and keep a running list of focus areas across mocks. The same item appearing in several mocks is the most important thing to work on.
Rerun the same round
The most useful mock is often the second attempt at a round that went badly. Work on the focus areas for a few days, then run the same type of round again, with a new prompt or the same one. The improvement is where the practice turns into skill, and seeing it is good for your confidence too.
How many mock interviews to do
There's no magic number. A reasonable approach:
- At least one mock per round type in your expected loop. Our guide to what an interview loop is covers the usual rounds.
- More for the rounds you find hardest. If system design is your weakest round, it deserves three mocks, not one.
- One full-length practice day if your final loop is several rounds back to back, so you know what the fourth interview feels like.
Spread them out. A mock every few days, with solo practice and study in between aimed at the focus areas, works better than five mocks in one weekend.
Mock interviews by round
Some round-specific tips:
- Recruiter screen: time your background and "why this role". See what to expect in a recruiter screen.
- Live coding: ask the interviewer to watch for silent stretches and for whether you tested your code. See how to prepare for a live coding interview.
- System design: ask them to change a requirement mid-design. See our 45-minute system design framework.
- Behavioural: ask them to dig with "what did you do?" until the rehearsed version runs out. See the STAR method for software engineers.
- Negotiation: ask them to push back and go quiet after you name a number. See how to negotiate a software engineer offer.
Practising with an AI interviewer
Finding someone to run mocks regularly is the hardest part. That's what Hardmode is for: an AI mock interviewer that reads the job description (and your CV, if you add one), runs a realistic round at the difficulty you choose, pushes back with follow-ups, and gives written feedback afterwards with what went well, focus areas, and a next step. It doesn't replace practising with people, but it means you can run a mock on a Tuesday evening without booking anyone. Each available round type can be practised on its own or as part of a plan built from a job posting.