Question library
Questions from real interviews. Drill any of them by voice in a couple of minutes, with an interviewer, a score and feedback.
Give me an example of when you did something useful at work that nobody asked you to do.JuniorTell me about a time when someone on your team didn't finish their part of the work on time, and your task depended on it. What did you do?JuniorTell me about a time when you had several urgent tasks at once. How did you decide where to start?JuniorTell me about a time you disagreed with a colleague or a classmate about how to do a task. How was it resolved?JuniorTell me about a time you got a task with a vague brief. How did you figure out what needed to be done?JuniorTell me about a time you got critical feedback on your work. How did you react to it?JuniorTell me about a time you got stuck on a task and couldn't solve it on your own. What did you do?JuniorTell me about a time you had to quickly get up to speed on something completely new to you.JuniorTell me about a time you made a mistake at work or in school. What happened next?JuniorTell me about the project or task you're most proud of.JuniorA registration form has an "Age" field that accepts whole numbers from 18 to 65. What checks would you come up with for this field, and how would you choose the specific values?JuniorExplain how a hash table works and why lookup in it is O(1) on average. What is a collision, and when does a hash table degrade?JuniorExplain how a heap works and how to use it to find the k largest elements. Why is a heap of size k better than a full sort?JuniorExplain how a variable-length sliding window works and how sliding window problems differ from prefix sum problems. When won't a sliding window work?JuniorExplain how an event propagates in the DOM and what event delegation is.JuniorExplain how async and await work in Python. What happens if you call a regular time.sleep inside a coroutine?JuniorExplain how backtracking works, using the example of generating all subsets, and what its complexity is.JuniorExplain how the event loop works in JavaScript. And what gets printed to the console if a script has, one after another, a console.log, a setTimeout with zero delay, and a Promise.resolve().then?JuniorExplain how to find the order in which to run tasks that have dependencies (topological sort), and how to detect a cycle along the way.JuniorExplain how to reverse a linked list in place, and why a dummy head is used in linked list problems. What's the time and space complexity?JuniorExplain how you approach a problem with dynamic programming: how you choose the state, the transition and the base case. Show it on the climbing stairs problem or the house robber problem.JuniorExplain in simple terms what a p-value is.JuniorExplain the difference between INNER JOIN, LEFT JOIN and FULL OUTER JOIN.JuniorExplain the difference between depth-first and breadth-first tree traversal: how each one is implemented, what their space complexity is, and in which problems you'd choose BFS.JuniorExplain the two-pointer technique: when does it apply, why does it give O(n) instead of O(n²), and what example would you use to show it in an interview?JuniorExplain what Big O notation is and how to estimate the complexity of an algorithm. Why is O(n log n) better than O(n²) in practice, and why don't we write constants inside the O?JuniorExplain what a monotonic stack is and how it helps find the next greater element for every number in O(n).JuniorExplain what binary search on the answer is, and how you can tell that a problem can be solved with binary search even when there's no sorted array in it.JuniorHow are primitive types in Java different from wrapper classes, and what is autoboxing?JuniorHow do automated tests fit into continuous integration, and what happens when a test fails in the pipeline?JuniorHow do you decide which tests are worth automating and which are better left manual?JuniorHow do you find and handle missing values in pandas?JuniorHow do you write tests with pytest? Tell me about fixtures and how to replace an external dependency in a test.JuniorHow do you write unit tests in Java, and what is Mockito for?JuniorHow does HTTP caching work in the browser?JuniorHow does a HashMap work internally? What happens when you call put?JuniorHow does memory management work in Python? How are objects that are no longer needed removed?JuniorHow does prototypal inheritance work in JavaScript?JuniorHow does the @Transactional annotation work in Spring?JuniorHow does the Stream API work, and what role do lambdas play in it?JuniorHow is Django different from FastAPI? What kinds of projects would you choose each one for?JuniorHow is reflow different from repaint, and why does frequent reflow hurt performance?JuniorHow is testing a mobile app different from testing a website?JuniorHow would you calculate user retention for a mobile app?JuniorHow would you plan an A/B test of a new checkout button in an online store?JuniorImagine a function add with a parameter items whose default value is an empty list. The function appends an element to that list and returns it. What happens if you call it twice in a row without passing the second argument?JuniorImagine a query against a large table is running very slowly. Where would you start investigating?JuniorIn TypeScript, how is the unknown type different from any?JuniorIn TypeScript, what's the difference between interface and type?JuniorIn an online store, the discount depends on three conditions: whether the customer has a loyalty card, whether the order total is over $100, and whether this is their first order. How would you design the tests so that you don't miss a single combination?Junior
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