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A product-based company builds and sells its own software or online service, such as an app, a platform or a cloud product. These companies are often seen as hard to enter because they test problem solving closely. This guide explains what is tested and gives a plan you can follow without needing any special background.
Python, Java or C++. Pick one and know it deeply.
Arrays, strings, hash maps, stacks, queues, trees.
Easy first, then medium, a few every day.
Something finished that you can explain.
Solve aloud with a friend and review mistakes.
What these companies usually test
Entry-level interviews at product companies often have these parts. The mix depends on the role and the company, so check the job post.
| Part | What it looks like |
|---|---|
| Online coding test | Two or three problems with a time limit |
| Coding interviews | Solve a problem on a shared screen, explaining as you go |
| Role-specific round | For data roles: SQL, data modelling or a pipeline question |
| Project and behaviour | Your project, how you work in a team, why this company |
Build the foundation first
Pick one language and learn it well enough that syntax does not slow you down. Then study data structures in this order: arrays and strings, hash maps and sets, stacks and queues, sorting and searching, linked lists, trees, and then basic graphs. Learn the idea before you solve problems. For each structure, know what it is, what it costs to use, and when you would choose it.
If you are aiming at data roles, the Python practice page and the Python interview questions guide cover the language side, and SQL practice covers the database side.
How to practise problems
- Easy first. Solve many easy problems until the basic patterns feel normal.
- Think before you code. Say the approach, the time cost and a small example before you write.
- Review. After each problem, compare your answer with a better one. Write the idea in a note.
- Repeat. Return to problems you could not solve after a week.
- Time yourself. Aim to finish an easy problem in about 20 minutes and a medium problem in about 35.
Quality beats count. Fifty problems you understand well help more than three hundred you copied.
SQL, design and data topics for data roles
Data roles at product companies add SQL and pipeline design. Practise joins, GROUP BY and window functions until you can write them without help. Learn how to design a simple pipeline: where the data comes from, how it is cleaned, where it is stored and how you would check it. The SQL interview questions guide shows the question types that repeat, and the company guides such as Google and Amazon show the stages in more detail.
A 6-month plan
| Months | Focus |
|---|---|
| 1 | One language and arrays, strings and hash maps. Easy problems daily |
| 2 | Stacks, queues, sorting, searching. Easy and a few medium problems |
| 3 | Linked lists, trees and recursion. SQL joins and GROUP BY |
| 4 | Basic graphs, window functions. One project written up |
| 5 | Timed contests and mock interviews. Resume and LinkedIn ready |
| 6 | Apply widely, keep practising and review every interview |
Be realistic about the odds
Many students apply to these companies, and even strong candidates are rejected for reasons they cannot control. Apply to a wide range of companies, including smaller product firms and startups, so that practice turns into interviews. Treat each interview as practice. Write down every question you were asked, and use it to improve.
Where to start today
Pick your language. Solve two easy array problems today, and write the approach in one or two lines before you code.