Quick Answer
URL shortener interview phrases in English: separate create vs redirect, encode IDs clearly, then say why the read path needs a cache before the database.
Diagrams and what to say while drawing
Narrate each figure out loud. Point to the box you are talking about.
What to say on figure 1
Create path: client → API → ID service → DB.
What to say on figure 2
Redirect path: client → API → cache/DB → 302.
What to say on figure 3
Show base62 encoding of an ID.
What to say on figure 4
Show cache sitting on the redirect hot path.
Key vocabulary
| Term | Plain meaning | Say it in an interview |
|---|---|---|
| Short code | Compact ID in the URL | “The short code maps to the long URL.” |
| Redirect | Send the client to the long URL | “The read path is a redirect.” |
| Base62 | Encode IDs with 0-9a-zA-Z | “I’d encode the ID in base62.” |
| Collision | Two URLs get the same code | “We must handle hash collisions.” |
ESL English phrases and transitions
Clarify
- “What’s the expected create QPS versus redirect QPS?”
- “Do links expire, and do we need click analytics?”
Propose and check in
- “The next bottleneck is X, so I would add Y.”
- “Does this level of detail work, or should I go deeper?”
Tradeoffs
- “The advantage is simplicity; the downside is…”
- “I’d choose A over B because…”
Key English language pitfalls
| Pitfall | Sounds like | Say instead |
|---|---|---|
| Custom alphabet talk forever | Lost in detail | One sentence on base62 is enough |
| No collision plan | Incomplete | Mention uniqueness checks or ID-based codes |
| Summary | Every new box needs one spoken reason. | |
Common English mistakes
| Mistake | What the interviewer concludes | Better English |
|---|---|---|
| Forgetting redirect English | Unclear UX | “We return a 302 redirect to the long URL.” |
| Ignoring read/write skew | Wrong bottleneck | Say redirects are the hot path |
What the interviewer is testing
This is a communication test as much as a design test. Can you explain a url shortener as a calm collaboration?
Interviewers listen for structure, tradeoffs, and clear English under pressure.
Key takeaway
Your job is to narrate decisions the interviewer can follow and challenge — not to dump tools.
How to open the problem in English
Opening script you can practise aloud
- “What’s the expected create QPS versus redirect QPS?”
- “Do links expire, and do we need click analytics?”
Watch Out
Do not open with a finished architecture. Show the path.
Url shortener system design
Use this sequence for url shortener system design. For each stage, say what changes, why, and what can still go wrong.
APIs
POST create short URL; GET redirect by code.
Code generation
Hash the long URL or encode a unique ID in base62.
Storage
Store code → long URL; cache hot redirects.
Scale
Redirects dominate; keep the read path extremely fast.
Weak vs strong answers
Weak
“Hash the URL and done.”
Strong
“I’d generate a unique ID, encode it in base62 for the short code, store the mapping, and cache redirects because reads dominate.”
Metrics and how to say numbers
| Write | Say |
|---|---|
| 7-character code | a seven character code |
| 100:1 read/write | about one hundred redirects per create |
Follow-up questions you will get
Likely follow-ups
- “How do you prevent abuse?” → “Rate-limit creates and validate destination URLs.”
Practice drill
Checklist
- APIs
- Code gen
- Redirect path
- Cache reason
“If you can explain a url shortener without notes, you are ready to draw it in an interview.”
Answer frameworks you can reuse
Use these spoken templates under pressure. Fill the blanks — do not invent a new structure mid-interview.
Framework 1 — Whole answer
Clarify → High-level → Deep dive → Check-in.
Framework 2 — Each component (B-C-B-C)
Bottleneck → Component → Benefit → Cost.
Framework 3 — Now → Breaks → Next
Current design → failure mode → next upgrade.
Framework 4 — Draw → Name → Why → Risk
Narrate every box as you draw it.
Interview tip
Pick one framework and stay inside it. Switching structures mid-talk makes English sound messy.
Frequently Asked Questions
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