Technical interview preparation: a study plan for coding and system design

What technical interviews look like in 2026

Most engineering roles at mid-size and large companies run three to five rounds. A typical pipeline includes a recruiter screen, one or two coding rounds, a system design round, and a behavioural round. Some companies add a take-home project or a debugging exercise.

Coding rounds are usually 45 to 60 minutes on a shared editor such as CoderPad or LeetCode's interview mode. System design rounds run 45 to 60 minutes and are open-ended. Behavioural rounds use the STAR format and last 30 to 45 minutes.

Knowing the format matters because it shapes how you allocate study time. If you are applying for a senior role, system design carries more weight. If you are applying for a junior or new-grad role, coding fundamentals and communication matter most.

How to structure your study plan by week

Six weeks is enough time for most candidates who can study one to two hours on weekdays and three to four hours on weekends. Eight weeks is better if you have not coded regularly in the past year.

Split the plan into three phases: foundations, depth, and simulation.

1. Weeks 1 and 2 (foundations): Review core data structures and algorithms. Cover arrays, strings, hash maps, linked lists, stacks, queues, trees, and graphs. Solve 30 to 40 easy problems on LeetCode, focusing on pattern recognition rather than memorising solutions.
2. Weeks 3 and 4 (depth): Move to medium problems. Target the patterns that appear most often: sliding window, two pointers, binary search, BFS and DFS, dynamic programming basics, and heap problems. Aim for 40 to 60 medium problems across these patterns.
3. Weeks 5 and 6 (simulation): Do timed mock interviews. Solve problems under 35 minutes, talk through your thinking out loud, and review your solutions after. Add one system design session per week and two behavioural practice sessions.

Coding round: what to practise and how

The goal in a coding round is not just a correct solution. Interviewers assess how you think, how you handle edge cases, and whether you communicate clearly under pressure.

Before writing any code, spend two to three minutes clarifying the problem. Ask about input size, edge cases, and expected output format. This signals seniority and prevents wasted effort.

After you have a working solution, always discuss time and space complexity using Big O notation. A brute-force solution with a clear explanation of its trade-offs is better than a clever solution you cannot explain.

For language choice, Python is the most common in 2026 for its concise syntax. Java and C++ are fine. TypeScript is increasingly accepted. Pick one language and stick to it throughout your preparation.

• LeetCode Blind 75 list: a widely used set of 75 problems covering the most common patterns
• NeetCode 150: an extended list with video explanations, good for visual learners
• Pramp and Interviewing.io: free and paid platforms for live mock interviews with peers or engineers
• AlgoExpert: structured video walkthroughs if you prefer guided learning over self-study

System design round: a repeatable framework

System design rounds test whether you can translate vague requirements into a scalable architecture. There is no single correct answer. The interviewer wants to see structured thinking and awareness of trade-offs.

Use a consistent framework for every question. Start by clarifying requirements: functional requirements first, then non-functional ones such as scale, latency, and availability. Estimate scale before drawing anything. Then design the high-level architecture, drill into one or two components, and discuss trade-offs.

Common topics in 2026 include designing a URL shortener, a rate limiter, a notification service, a distributed cache, and a social media feed. Study each of these at least once.

Read the free chapters of the System Design Interview books by Alex Xu. They are the most cited resource in this space and cover the framework above in detail. Supplement with the ByteByteGo newsletter for current patterns.

• Clarify scale early: ask for daily active users, read-to-write ratio, and latency requirements
• Know the basics of SQL vs NoSQL trade-offs, CDN usage, load balancing, and caching strategies
• Be able to explain CAP theorem in plain language without memorising a textbook definition
• Practice drawing diagrams quickly; a whiteboard or Excalidraw works well for remote interviews

Behavioural round: preparing STAR stories

Behavioural rounds are not a formality. At many companies, a poor behavioural score can block an offer even if your coding was strong.

Prepare six to eight stories from your work history using the STAR format: Situation, Task, Action, Result. Each story should be two to three minutes when spoken aloud. Cover themes such as conflict resolution, a project you led, a time you failed and what you learned, and a time you influenced without authority.

Write your stories down before practising them verbally. This forces you to be specific about numbers and outcomes. Vague answers such as 'we improved performance' are weaker than 'we reduced p99 latency from 800ms to 120ms by switching to an async queue'.

Research the company's stated values before each interview. Amazon uses Leadership Principles explicitly. Google, Meta, and most Australian and UK tech companies use competency-based questions tied to their engineering levels. Tailor one or two stories to the values you find.

Using an interview assistant during live rounds

Some candidates use real-time support during interviews. Break-In Bad's interview assistant listens to the interviewer's questions and shows suggested answers only you can see, even on a shared screen. This can be useful for behavioural questions where you want a prompt to recall the right story, or for system design when you want a checklist of components to cover.

It is not a substitute for preparation. Interviewers notice when answers feel disconnected from the conversation. Use it as a safety net, not a script.