· Scenarios · 2 min read
Scenario: Designing a URL Shortener (Interview Question)
A practical scenario guide on designing a scalable URL shortener like Bitly, and how to effectively communicate system architecture during engineering interviews.
You are in a System Design Interview. The interviewer looks at you and says: “Design TinyURL. It needs to handle 100 million writes per month and be highly available.”
Your mind starts racing. You know you need a database. You know you need a hashing algorithm. You know you need a cache.
But if you just start talking you will ramble. If you try to draw on the Zoom whiteboard with your mouse you will draw a mess.
You need to show you are an architect. You need a diagram.
The Challenge: Typical system design prompt
The challenge isn’t just knowing the answer. It is communicating the answer effectively under pressure.
You need to show:
- High Level: The user flow.
- Scale: How you handle the read/write load.
- Data Model: How you store the mappings.
The Workflow:
Here is how you use AI Diagram Maker to ace the interview.
Drawing the high-level components (API, DB, Cache)
You share your screen. You open the tool. You start typing.
“User connects to Load Balancer. Load Balancer connects to Web Server. Web Server connects to Database.”
The diagram appears. You point to it. “First we handle the basic flow.”
The interviewer nods. “Okay but reads are 100x higher than writes.”
You update the prompt. “Add a Redis Cache between Web Server and Database. Add Read Replicas to the Database.” The diagram updates. You have visually demonstrated your understanding of caching strategies.
Adding the Key Generation Service
Then you tackle the tricky part. Generating unique keys.
“If we generate keys on the fly we might get collisions. I propose a Key Generation Service (KGS).”
You add a new box. “Add a Key Generation Service that pre-loads keys into the Web Server memory.”
The AI draws the new component. The diagram now looks complex and professional.
The Result: A complete architectural diagram in minutes
By the end of the 45 minutes you have a complete architecture diagram. It shows the Load Balancer, the Cache, the Database Sharding strategy, and the KGS.
You didn’t spend a single second fighting with alignment tools. You spent 100% of your time demonstrating your engineering judgment.
The interviewer takes a screenshot of your diagram for their feedback notes. You passed.
Practice your design. Don’t wait for the interview. Use AI Diagram Maker to practice common system design questions. It is the best way to build muscle memory for high-stakes architecture.
