First design walkthrough (URL shortener) in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the main component responsible for generating short URLs.

HLD

The core component that generates the short URL is called the [1] service.

Drag options to blanks, or click blank then click option'

ALoad Balancer

BURL Resolver

CURL Shortening

DDatabase

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing the URL Resolver with the URL Shortening service.

Thinking the database generates the short URL.

The URL Shortening service is responsible for creating the short version of the original URL.

2fill in blank

medium

Complete the code to describe the key-value store used for mapping short URLs to original URLs.

HLD

The system uses a [1] to store the mapping between short URLs and original URLs for fast lookup.

Drag options to blanks, or click blank then click option'

Arelational database

Bkey-value store

Cfile system

Dmessage queue

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing relational database which is slower for simple key lookups.

Choosing message queue which is for asynchronous processing.

A key-value store is ideal for fast retrieval of the original URL using the short URL as the key.

3fill in blank

hard

Fix the error in the request flow description for redirecting short URLs.

HLD

When a user clicks a short URL, the system [1] the original URL from the database and redirects the user.

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Areads

Bdeletes

Cwrites

Dupdates

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking the system writes or updates during redirect.

Confusing read with delete operation.

The system reads the original URL from the database to redirect the user correctly.

4fill in blank

hard

Fill both blanks to complete the description of the short URL generation logic.

HLD

To generate a unique short URL, the system uses a [1] to create a unique ID and then [2] it into a short string.

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Acounter

Bhashes

Cdatabase

Dencodes

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'hashes' instead of 'encodes' for the second blank.

Using 'database' instead of 'counter' for the first blank.

The system uses a counter to generate a unique ID and then encodes it into a short string for the URL.

5fill in blank

hard

Fill all three blanks to complete the description of scaling the URL shortener system.

HLD

To handle high traffic, the system uses a [1] to distribute requests, multiple [2] for storage, and [3] caching to speed up lookups.

Drag options to blanks, or click blank then click option'

Aload balancer

Bdatabases

Cin-memory

Dsingle server

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'single server' which does not scale well.

Confusing caching with database storage.

A load balancer distributes incoming requests, multiple databases store data reliably, and in-memory caching speeds up data retrieval.