React Developer Interview Experience: AI Screening, Machine Coding & Output Questions (2026)
A few days ago I interviewed for a frontend developer role at a startup. The process had an AI screening round followed by a technical round covering theory, output prediction, machine coding, debugging, and optimization. I don't know yet whether I'll move forward, but I'm sharing everything I remember in case it helps you prepare.
Round 1 was the AI-Powered Screening
This round was fully AI-driven, with no human interviewer. It covered basic React questions, and I cleared it. Expect fundamentals like:
• useState and how state updates work
• useEffect and its dependency array
• Basic component and props questions
Tip: Answer clearly and concisely. Since there's no human to read your tone, being direct and structured helps.
Round 2 was the Technical Interview
I was called for this round about five days after the screening. It was the more intense one, and it had five parts.
Part 1: Theory questions
These came first and I felt confident:
• Why use React?
• What does "optimization" mean in React?
• How does the virtual DOM diffing work?
• Context API vs Redux: when would you use one over the other?
• What does Babel do?
Part 2: Input/Output questions (the hardest part for me)
I was shown code snippets and asked to predict the output. They combined function currying, closures, IIFEs, and higher-order functions. Predicting the output wasn't enough. The follow-ups were about the reasoning, like "what would change if this variable were declared elsewhere?"
A follow-up like "what if count were declared outside the IIFE?" tests whether you understand scope and who can modify the variable.
My advice for you all would be to build a real understanding of closures, scope, and this instead of memorizing definitions. The follow-up questions expose memorized answers quickly.
Part 3: Machine coding (with some styling)
I was asked to build a restaurant cart calculator mini-app. Users could add food items and adjust quantities. Tax had to be applied to each item after the packaging charge but before the delivery charge, plus a few more rules I don't fully remember. It wasn't as straightforward as it sounds.
The real task had more rules, but the main lesson was the same: keep the calculation logic in one pure function, separate from the UI, and derive totals from state instead of storing them. That made it easy to adjust when a rule changed.
If you want to practice something very close to this, try Order Bill Calculator Problem.
Part 4: Debugging and lazy loading
I got buggy code that fetched about 1,000 todos from an API and rendered them. After I fixed the bug, they asked me to show only 20 items initially, without pagination.
I implemented lazy loading with scroll-based loading. I'm not certain it was the expected approach, but here is the idea:
Other valid options would be a "Load more" button or list virtualization. It's worth being ready to explain the trade-offs between them.
Part 5: Re-render optimization
The last task: several components were imported into App.jsx, each logging a rendered {n} times message. A button showed Count is {count} and incremented on click. Clicking the button should not re-render or log in the other components, and vice versa.
This is a common optimization problem. I solved it using React.memo, useCallback, and useMemo.
• React.memo stops a component from re-rendering when its props haven't changed.
• useCallback keeps function props referentially stable, so memo actually works.
• useMemo does the same for objects or expensive values passed as props.
One thing to know: if a child receives no props, React.memo alone is enough. useCallback and useMemo matter when you pass functions or objects down.
What I'd do differently
• Spend more time on output-prediction practice. It was the section I was least ready for.
• Practice explaining my reasoning out loud while coding, not only after.
• Revisit lazy loading and virtualization so I can compare approaches with confidence.
Topics to prepare
[1.] Closures, scope, currying, IIFEs, higher-order functions
[2.] useState, useEffect and its dependency array, useRef
[3.] React.memo, useCallback, useMemo and when each one helps
[4.] Context API vs Redux trade-offs
[5.] Virtual DOM and reconciliation basics
[6.] Small machine-coding apps (cart, todo, search with debounce)
[7.] Lazy loading and list performance
I'm not sure whether I'll advance to the next round, but I hope this helps your preparation. If you'd like more practice questions from this interview, let me know in the comments and I'll add links to this post.
Best of luck, and keep practicing!
