Walleye Capital·Software Engineer·Technical Phone Screen
Jun 2026
Technical screen at Walleye Capital where they handed me a set of React files with bugs baked in and asked me to work through them live. Eight categories of issues, one after another. Not a vibe check, more like a gauntlet.
- You're given a React component where a useEffect or useCallback has a stale closure. Identify the symptom, root cause, and minimal fix.
- A component is mutating state directly instead of using immutable updates. Walk through how you'd spot it and fix it.
- List items in a component are using incorrect or unstable key props. What goes wrong and how do you fix it?
- A component is causing a re-render storm due to unstable object or function references passed as props or through context. Debug it.
- There's an async race condition in a useEffect. A fetch kicks off, the component unmounts or re-renders before it resolves, and stale results get applied. How do you handle it?
- A form input is switching between controlled and uncontrolled. What's the bug and what's the fix?
- Conditional rendering using && is showing a 0 on screen instead of nothing. Why does this happen and how do you fix it?
- An event handler isn't firing correctly due to a binding issue or prop-drilling mistake. Identify and fix it.
“This one I actually felt okay on.”