How to prepare for a technical coding interview
In a technical interview, you need to make your reasoning visible alongside code or an architecture sketch. Prepare a way to clarify the problem, compare alternatives and check your solution. These steps work for rehearsing both coding and system design conversations.
1. Clarify the problem before solving it
Restate what the solution needs to do. Identify inputs, outputs and constraints. Ask about data volume, whether order matters and what should happen with empty or invalid inputs. Keep stated requirements separate from assumptions you are proposing.
In system design, ask which functions are needed and what matters most: latency, availability, consistency or cost. Choose a database or queue after you can explain the problem it solves.
“To confirm: we need the first repeated value in input order. What should we return if there are no duplicates? Can we use additional memory?”
2. Explain a simple solution and its limits
Start with an approach you can defend. Then explain what you would change if a constraint requires it. Finding a duplicate by comparing each element with earlier elements usually takes quadratic time. Using a set gives average constant-time lookups for previously seen values, at the cost of additional memory.
State your assumptions: that average depends on the set implementation and does not describe every possible case. If positions matter, you may need a map instead of a set. If the input is already sorted, comparing neighboring elements offers another option.
For an architecture, first sketch a request's path. Add caches, queues or replicas when you can explain the need they address and the new problem they introduce.
3. Check concrete cases before finishing
Walk through a small input by hand and explain which state changes at each step. For the duplicate example, try an empty list, a single element, a list without duplicates and one with a duplicate at the end. Ask whether null values are allowed before deciding how to handle them.
- Does the output match the requirement you confirmed?
- Did you accidentally change the order or the input data?
- Can you justify your solution's time and memory costs?
- What happens if a dependency fails or the same request arrives twice?
The last question is particularly useful in system design. Explain how you would detect a failure and what can be recovered. Do not assume retrying is always safe.
4. Rehearse explaining a decision
Choose an exercise and talk through requirements, approach, checks and alternatives aloud. If you get stuck, return to the last step you understood and describe what is missing. A specific question is more useful than switching solutions without explaining why.
For project questions, prepare a real story: the constraint you faced, the decision you personally made, an alternative you rejected and what you learned. Use a number only if you can support it.
If English is an additional language for you, rehearse phrases such as “The trade-off is…” and “This assumes that…”. The English job interview guide includes an introduction structure and clarification phrases.
5. Use AI assistance thoughtfully
PasaRonda supports technical interviews: you can attach a screenshot of a prompt and receive an approach, alternatives and diagrams after the brief cues. The screenshot is sent only when you choose to send it. Check that it does not contain information unrelated to the exercise.
Check every assumption and step before using a suggestion. AI does not certify code correctness or replace your knowledge. Confirm which tools the interview permits, and use this guide to rehearse independently too.