Global server load balancing (GSLB) in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the main purpose of GSLB.

HLD

The primary function of GSLB is to [1] user requests across multiple data centers.

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

Adelete

Bignore

Cstore

Droute

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'store' or 'delete' which do not relate to request handling.

GSLB routes user requests to the best data center to balance load and improve performance.

2fill in blank

medium

Complete the code to specify a key factor GSLB uses to decide routing.

HLD

GSLB often uses [1] information like server health and proximity to route traffic.

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

Ahistorical

Brandom

Creal-time

Dstatic

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'random' or 'static' which do not reflect dynamic routing.

GSLB uses real-time data such as server health and network latency to make routing decisions.

3fill in blank

hard

Fix the error in the GSLB request flow step.

HLD

User DNS query is resolved by [1] to direct traffic to the optimal data center.

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

Alocal DNS server

Brandom server

Cold DNS cache

Dbackup server

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'random server' or 'old DNS cache' which cause incorrect routing.

The local DNS server resolves queries using GSLB logic to route users correctly.

4fill in blank

hard

Fill both blanks to complete the GSLB health check logic.

HLD

GSLB performs [1] checks and [2] monitoring to ensure server availability.

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

Aperiodic

Brandom

Ccontinuous

Dmanual

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'random' or 'manual' which are not automated or consistent.

GSLB uses periodic health checks and continuous monitoring to keep track of server status.

5fill in blank

hard

Fill all three blanks to complete the GSLB failover mechanism.

HLD

If a data center [1], GSLB [2] traffic to a [3] data center.

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

Afails

Bredirects

Chealthy

Ddelays

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'delays' which causes downtime instead of failover.

When a data center fails, GSLB redirects traffic to a healthy data center to maintain service.

Practice

1. What is the primary purpose of Global Server Load Balancing (GSLB)?

easy

A. To balance load only within a single data center

B. To direct user requests to the best global server based on location and health

C. To encrypt data between servers globally

D. To store user data in a centralized database

Solution

1. Step 1: Understand GSLB's role in system design

   GSLB directs traffic globally to optimize speed and availability by choosing the best server.

2. Step 2: Differentiate GSLB from local load balancing

   Local load balancing manages traffic inside a data center, while GSLB manages traffic across data centers worldwide.

3. Final Answer:

   To direct user requests to the best global server based on location and health -> Option B

4. Quick Check:

   GSLB = directs users globally [OK]

Hint: GSLB chooses best global server, not just local load [OK]

Common Mistakes:

• Confusing GSLB with local load balancing
• Thinking GSLB handles data encryption
• Assuming GSLB stores user data centrally

2. Which of the following is a correct component used in GSLB architecture?

easy

A. Global DNS server with health checks

B. Single local load balancer without DNS

C. Centralized database for user sessions

D. Static IP routing without failover

Solution

1. Step 1: Identify key GSLB components

   GSLB uses global DNS servers that perform health checks to route users to healthy servers.

2. Step 2: Eliminate incorrect options

   Local load balancers alone don't handle global routing; centralized databases and static IP routing don't provide dynamic failover.

3. Final Answer:

   Global DNS server with health checks -> Option A

4. Quick Check:

   GSLB = global DNS + health checks [OK]

Hint: GSLB needs DNS with health checks, not just local balancers [OK]

Common Mistakes:

• Ignoring the role of DNS in GSLB
• Confusing local load balancer as GSLB
• Assuming static routing works for failover

3. Consider a GSLB setup with three data centers: US, Europe, and Asia. If the US data center is down, where will the DNS direct a user from Europe?

medium

A. To the closest healthy data center, Europe or Asia

B. To a random data center without health checks

C. To the US data center regardless of health

D. To the Asia data center only

Solution

1. Step 1: Understand GSLB health check impact

   If the US data center is down, GSLB excludes it from routing decisions.

2. Step 2: Determine routing for European user

   The DNS directs the user to the closest healthy data center, which could be Europe or Asia depending on proximity and health.

3. Final Answer:

   To the closest healthy data center, Europe or Asia -> Option A

4. Quick Check:

   GSLB routes to closest healthy server [OK]

Hint: GSLB skips unhealthy centers, picks closest healthy [OK]

Common Mistakes:

• Routing to down data center ignoring health
• Choosing random data center without checks
• Always routing to Asia regardless of location

4. A GSLB system is not redirecting traffic away from a failed data center. What is the most likely cause?

medium

A. User's browser cache is cleared

B. DNS TTL is set to zero

C. Load balancer inside data center is overloaded

D. Health checks are not configured or failing silently

Solution

1. Step 1: Analyze GSLB failure to redirect

   If traffic is not redirected from a failed data center, health checks likely are missing or not reporting failures.

2. Step 2: Evaluate other options

   DNS TTL zero causes frequent lookups but doesn't prevent failover; local load balancer overload or browser cache do not affect global DNS routing.

3. Final Answer:

   Health checks are not configured or failing silently -> Option D

4. Quick Check:

   Health checks missing = no failover [OK]

Hint: Check health checks first if failover fails [OK]

Common Mistakes:

• Blaming DNS TTL for failover issues
• Confusing local load balancer issues with GSLB
• Assuming browser cache affects server routing

5. You need to design a GSLB system for a global video streaming service. Which combination best improves user experience and reliability?

hard

A. Single global load balancer without DNS + static IP routing

B. Local load balancers only with no global routing

C. Global DNS with health checks + local load balancers + geo-proximity routing

D. DNS-based routing without health checks or load balancing

Solution

1. Step 1: Identify key GSLB features for video streaming

   Global DNS with health checks ensures users reach healthy servers; local load balancers distribute load inside data centers.

2. Step 2: Consider geo-proximity routing benefits

   Routing users to nearest data center reduces latency, improving streaming quality and reliability.

3. Step 3: Eliminate less effective options

   Single load balancer or no health checks cause bottlenecks or failover issues; local only misses global optimization.

4. Final Answer:

   Global DNS with health checks + local load balancers + geo-proximity routing -> Option C

5. Quick Check:

   Combine global DNS, health checks, local balancers, geo-routing [OK]

Hint: Combine global DNS, health checks, and geo-routing for best results [OK]

Common Mistakes:

• Ignoring health checks in DNS routing
• Using single load balancer for global traffic
• Skipping geo-proximity routing for latency