The morning of your interview.

The night before

1. Stop adding new material. Whatever you don't know tonight, you won't know tomorrow. Re-read your own notes for 30 minutes. Anything beyond that is anxiety, not preparation.
2. Pack your gear. Laptop charger. Phone charger. Backup pen and paper. Water bottle. ID for the office (if in-person). Reading glasses.
3. Pick your clothes. Comfortable, neat. Decisions in the morning are decisions you can't make about the round.
4. Check the calendar. Time zones, video links, dial-in. Phone the interviewer's recruiter if anything is ambiguous; do it tonight, not in the morning.
5. Set two alarms. One on your phone, one on a clock or a second device. Hotel alarm clocks are unreliable; trust nothing.
6. Sleep by midnight. Caffeine clears in ~6 hours; alcohol degrades sleep quality even at one drink. Both are easier to forgo for one night than to regret.

Two hours before the first round

1. Wake up early enough to be awake. Most people need 90 minutes between wake-up and clear thinking. If your first round is 10:00, be up by 8:30.
2. Eat protein + slow carbs. Not just coffee. Eggs and toast, or oats with nuts, or yoghurt with granola. Sugar spikes followed by crashes are bad for working memory.
3. Walk for fifteen minutes. Outside, ideally. Light + movement + fresh air resets cortisol. Do not check Slack or email.
4. Review the trade-offs cheat sheet below. Nothing else. New material at this hour is anxiety, not study.
5. Glass of water every 30 minutes. Mild dehydration costs ~5% on cognitive tests. You do not feel it; it shows up anyway.

Twenty minutes before

1. Tool check. Camera works. Mic works. Speaker volume. Browser tabs open: your editor, the company's interview link, a blank Excalidraw or Whimsical board, your notes file.
2. Close everything else. Slack, mail, music, notifications. The round needs the foreground.
3. Bathroom break. The 45-minute round will feel like four hours if you skip this.
4. Pen and paper at hand. Even if the round is on a whiteboard tool, having paper for capacity-math scratch saves time.
5. Three deep breaths. Diaphragmatic, not chest. Slows heart rate, drops baseline cortisol. Costs nothing.

During the round

1. Narrate before you draw. "Let me clarify the requirements first" — restate the question in your own words. Don't start drawing.
2. Watch your clock. Phone or watch face-up beside you (interviewers don't mind). Cross-reference against the seven phases.
3. Don't apologise for thinking. Ten seconds of silence to formulate is normal. "Let me think about that for a second" is fine; mumbled words to fill the void are not.
4. Pick the deep dive proactively. Don't wait for the interviewer to ask. "Of these four components, this one is where the design lives or dies because X — I'll go deep here."
5. If stuck, ask. "Am I going in the direction you expected?" gives the interviewer permission to redirect without it counting as a hint.
6. Own your trade-offs. "I chose SQL here because the access pattern is mostly keyed lookups; the trade-off is harder horizontal scaling, which I'd address by sharding by tenant if we hit it." Cost named; mitigation named.

Between rounds

1. Five minutes off. Water, bathroom, stand up. Look at the wall, not your screen.
2. Do not replay the previous round. It's done. Replaying degrades your performance on the next one.
3. Do not preview the next prompt. If you have the option to read prompts in advance, don't. It denies you the clarify phase, which is half the signal.
4. Reset, don't recover. The goal isn't to feel better about the previous round; it's to enter the next one fresh.

After the loop

1. Write down what you remember within an hour. Specifically: what you wish you had said, what you said well, what the interviewer pushed on. Notes you take an hour later are useful; notes you take a day later are mostly imagined.
2. Don't message the recruiter the same day. They've heard from every other candidate already. Sleep on it. Send a brief, concrete thank-you the next morning.
3. Don't replay the loop with friends. Use a journal or a single-page document for yourself. Talking the loop to death replaces real feedback with confabulation.
4. Sleep early. The cognitive cost of a full loop is real. Take the next morning slow.

Trade-offs cheat sheet (one-pager)

The trade-offs you most need on the tip of your tongue. None of these is novel; the value is in having them already cached, so the round doesn't burn a minute deriving them.

Numbers to know cold

See the full cheat sheets shelf for the printable A4 versions of these and other references.

Related on Semicolony

• Interview prep hub — back to the main page
• 45-minute system-design simulator
• Interview flashcards (100 cards across 6 categories)
• Mock-feedback rubric — score yourself after a round
• Company loop guide — what to expect at each FAANG-tier company
• L5 vs L6 vs staff differences
• Printable cheat sheets