What to work through
Work through a file browser as a spoken system design interview. Start by clarifying the scope, sketch a working design and explain the trade-offs behind your choices.
- Show a folder tree that opens folders as the person expands them
- List the files in the open folder, with name, size and date
- Open a file and show it in a way that fits its type
- Upload new files into the open folder, with progress
- Move through folders with links and the back button
Constraints to discuss
- A click on a folder or file answers within 200 milliseconds
- A folder of 1,000 files or more scrolls smoothly
- An upload survives a dropped connection without starting over
- The tree works by keyboard and with a screen reader
- A file from someone else never runs code in the page
Need a starting point?
Watch for these common gaps as you prepare:
- Fetching and drawing every file of a big folder at once
- Keeping the current folder only in page state, so back and reload lose it
- Sending a large file in one request with no way to resume
- Assuming the server got every byte that was sent
- Putting a stranger's HTML file straight into the page
Why this question is in the collection
These sources connect the problem to company interview reports or preparation guides. They do not guarantee what a company will ask you.
- Lyft: A frontend tip from February 2025: the frontend system design round was "harder than expected" and asked for a file management system like the files view of a GitHub repository.
- Adobe: A senior frontend engineer on the Gen Studio team reports "Design a file system" as the first round of the full loop, a system design round, in a loop from December 2025 to January 2026 posted about March 2026. The post gives no scope, so it may not have been a file browser.