CDN concept and usage in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the main purpose of a CDN.

HLD

A CDN primarily helps to [1] content closer to users.

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

Aencrypt

Bdelete

Ccache

Dcompress

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing caching with deleting content.

Thinking CDN encrypts content by default.

A CDN caches content on servers near users to reduce latency and improve load times.

2fill in blank

medium

Complete the code to show what a CDN reduces in network communication.

HLD

A CDN reduces [1] between the user and the origin server.

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

Asecurity

Bbandwidth

Cerrors

Dlatency

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing bandwidth with latency.

Thinking CDNs reduce security risks directly.

CDNs reduce latency by serving content from nearby servers instead of the origin server far away.

3fill in blank

hard

Fix the error in the description of CDN edge servers.

HLD

Edge servers in a CDN are located [1] the origin server to serve content faster.

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

Aclose to

Bfar from

Cinside

Dbehind

Attempts:

3 left

💡 Hint

Common Mistakes

Assuming edge servers are far from users.

Confusing edge servers with origin servers.

Edge servers are placed close to users, far from the origin server, to reduce latency.

4fill in blank

hard

Fill both blanks to complete the CDN request flow.

HLD

User requests content → DNS directs to [1] → [2] serves cached content if available.

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

Aedge server

Borigin server

CCDN

Dload balancer

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing origin server with edge server in DNS routing.

Thinking load balancer serves cached content directly.

The DNS directs the user to the edge server, which is part of the CDN and serves cached content.

5fill in blank

hard

Fill all three blanks to complete the CDN benefits list.

HLD

CDNs improve [1], reduce [2], and increase [3] for websites.

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

Aperformance

Blatency

Cavailability

Dcost

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up latency and availability.

Thinking CDNs primarily reduce cost.

CDNs improve performance, reduce latency, and increase availability by distributing content globally.

Practice

1. What is the primary purpose of a Content Delivery Network (CDN) in system design?

easy

A. To store copies of content closer to users for faster delivery

B. To increase the size of the main server's database

C. To replace the main server completely

D. To encrypt all user data end-to-end

Solution

1. Step 1: Understand CDN's role in content delivery

   A CDN caches copies of content at locations near users to reduce latency and speed up access.

2. Step 2: Compare options with CDN purpose

   Only To store copies of content closer to users for faster delivery describes storing content near users for faster delivery, which is the main CDN function.

3. Final Answer:

   To store copies of content closer to users for faster delivery -> Option A

4. Quick Check:

   CDN = content near users for speed [OK]

Hint: CDN = cache content near users to speed delivery [OK]

Common Mistakes:

• Thinking CDN replaces main server
• Confusing CDN with encryption service
• Assuming CDN increases database size

2. Which of the following is the correct way to describe how a CDN handles user requests?

easy

A. User requests always go directly to the origin server

B. CDN stores user credentials for authentication

C. CDN modifies user requests to change content

D. User requests are routed to the nearest CDN edge server if content is cached

Solution

1. Step 1: Understand CDN request routing

   CDNs route user requests to the closest edge server that has cached content to reduce latency.

2. Step 2: Evaluate options for request handling

   User requests are routed to the nearest CDN edge server if content is cached correctly states requests go to nearest CDN edge if cached; others are incorrect or unrelated.

3. Final Answer:

   User requests are routed to the nearest CDN edge server if content is cached -> Option D

4. Quick Check:

   CDN routes requests to nearest cache [OK]

Hint: Requests go to nearest cached CDN server, not origin [OK]

Common Mistakes:

• Assuming all requests hit origin server
• Believing CDN changes content on the fly
• Confusing CDN with authentication service

3. Consider a system using a CDN with edge servers in multiple regions. If a user in Europe requests a static image, which server will most likely serve the image?

medium

A. A CDN edge server located in Europe

B. The origin server located in the US

C. A random CDN edge server in Asia

D. The user's local device cache only

Solution

1. Step 1: Identify CDN edge server selection logic

   CDNs serve content from the closest edge server to the user to reduce latency.

2. Step 2: Match user location with server location

   A user in Europe will get content from a European CDN edge server if available, not from origin or distant servers.

3. Final Answer:

   A CDN edge server located in Europe -> Option A

4. Quick Check:

   User location matches nearest CDN edge server [OK]

Hint: User served by nearest CDN edge server geographically [OK]

Common Mistakes:

• Assuming origin server always serves content
• Choosing random or distant CDN servers
• Ignoring CDN edge server caching

4. A developer notices that users are still experiencing slow load times despite using a CDN. Which of the following is the most likely cause?

medium

A. The CDN is encrypting content which slows delivery

B. The CDN is not caching the content properly, causing requests to go to the origin server

C. The CDN is blocking user requests randomly

D. The CDN is storing user passwords insecurely

Solution

1. Step 1: Analyze slow load cause with CDN

   If CDN cache misses occur, requests go to origin server, increasing latency and slowing load times.

2. Step 2: Evaluate options for likely cause

   The CDN is not caching the content properly, causing requests to go to the origin server explains cache miss causing slow loads; others are unrelated or incorrect.

3. Final Answer:

   The CDN is not caching the content properly, causing requests to go to the origin server -> Option B

4. Quick Check:

   Cache miss = slow load [OK]

Hint: Slow CDN? Check if cache is missing content [OK]

Common Mistakes:

• Blaming encryption for speed issues
• Assuming CDN blocks requests randomly
• Confusing CDN with security storage

5. You are designing a global video streaming service. Which CDN usage strategy best improves performance and reduces origin server load?

hard

A. Disable CDN caching to ensure fresh content always

B. Cache only small static files like logos, serve videos directly from origin

C. Cache all static content including videos on CDN edge servers worldwide

D. Use CDN only for user authentication requests

Solution

1. Step 1: Identify content types for CDN caching

   Videos are large static files that benefit greatly from CDN caching near users to reduce latency and origin load.

2. Step 2: Evaluate CDN strategies for global streaming

   Caching all static content including videos on CDN edges worldwide improves performance and reduces origin server load.

3. Final Answer:

   Cache all static content including videos on CDN edge servers worldwide -> Option C

4. Quick Check:

   Cache large static files globally for best performance [OK]

Hint: Cache all static content globally on CDN edges [OK]

Common Mistakes:

• Caching only small files and ignoring videos
• Disabling CDN caching unnecessarily
• Using CDN for unrelated tasks like authentication