YOUR BRIEF
What to work through
Work through bitly as a spoken system design interview. Start by clarifying the scope, sketch a working design and explain the trade-offs behind your choices.
- Create a short link for a long URL
- Optionally choose a custom alias
- Optionally set an expiry time
- Visiting a short link redirects to the long URL
BEFORE YOU START
Constraints to discuss
- Every short code is unique
- Redirects answer in under 100 ms
- 99.99% availability for redirects
- Reads outnumber writes about 1000 to 1
Need a starting point?
Watch for these common gaps as you prepare:
- Using a prefix of the long URL as the code
- Choosing 301 by default and losing expiry and analytics
- A cache TTL longer than the link’s expiry
- Custom aliases and generated codes in separate namespaces that can collide
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.
- Google: Aced’s Google guide lists a TinyURL-style URL shortener among the questions Google candidates report.
- Amazon: First on Hello Interview’s list of the system design questions most asked at Amazon SDE III.
- Uber: PracHub lists an Uber report of "Design a Highly Available URL Shortener" from August 2026.