Frontend

How does the Event Loop work — what queues are there, and what is their execution order? Tell about microtasks, macrotasks, requestAnimationFrame, requestIdleCallback.

The API response may contain an error that should be displayed to the user next to the corresponding field.

Was this a B2B or B2C service? Were there metrics to track errors and user experience?

There is a tab filter. When switching tabs quickly, sometimes old values unrelated to the current tab are shown. What is the reason and how to fix it?

Write an implementation of the helper Promise.withResolvers() — a function that creates a Promise and returns an object with three properties: promise, resolve, and reject.

What can be done with images to optimize page performance?

Imagine a page with many cards and lazy loading (like on Stripchat). What corner cases do you see, what problems might arise, and what would you optimize? How does virtualization (React Window) work?

Look at this SSR code with a singleton i18n class. Find a serious problem that could spoil the HTML delivered to the user. How to fix it?

We cannot tag and version through CI/CD. The client may be one version, the backend another. What can be done in these conditions besides error monitoring through Sentry?

You need to design a road sign on a single div, including a small red notch on the right.

We have a large monorepo project with a unified release flow. We decided to split it and move the frontend to separate repositories with their own release cycle. This causes a version desynchronization problem between the backend and the client. How would you see a solution to this problem? How to organize work to be as protected as possible from failures in production?

Why do users not enter the Store and how to load users into the Store?

What reducers does the Store have, and is there a reducer for adding users?

What can block the first rendering in the browser after receiving HTML? What can be done about synchronous loading of JS and CSS?

Where was the normalized cache stored? Was it some kind of reactive one?

You mentioned that you reduced the number of repeated API requests by 42%. What exactly did you do and how did you measure the result?

Look at the function in the editor: it takes an array of keys and an object, and uses reduce to copy only the object with the specified keys. What would you name this function?

On navigating from the user list page to a specific user's page, there is a long load time (loader hangs for 2 seconds due to artificial delay). How can this situation be improved?

If you had a blank check, what would be the perfect form you would create? What approaches, technologies, and methods would you use (validation, error handling, UX, DX)?

We see that SSR does not respond for 2 seconds. What options are there to improve this?