Services and networking in Microservices - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Architecture

intermediate

Designing Service Communication in Microservices

You have three microservices: User, Order, and Inventory. Which communication pattern best reduces tight coupling and improves scalability?

A Using an asynchronous message broker for event-driven communication

B Synchronous HTTP calls directly between services for every request

C Embedding all logic into a single monolithic service

D Using shared database tables for communication between services

💡 Hint

Think about how services can work independently without waiting on each other.

Asynchronous message brokers allow services to communicate without waiting, reducing tight coupling and improving scalability.

❓ scaling

intermediate

Scaling Service Discovery in a Microservices Environment

You have 100 microservices instances running across multiple servers. Which approach best supports automatic service discovery and load balancing?

A Manually configure IP addresses of all instances in each service

B Use a centralized service registry with health checks and client-side load balancing

C Use DNS with static entries for each service instance

D Hardcode service endpoints in configuration files

💡 Hint

Consider how services can find healthy instances dynamically without manual updates.

A centralized service registry with health checks allows services to discover healthy instances dynamically and balance load efficiently.

❓ tradeoff

advanced

Choosing Between API Gateway and Service Mesh

Which statement best describes a key tradeoff when choosing between an API Gateway and a Service Mesh for microservices networking?

A API Gateway centralizes external client requests, while Service Mesh manages internal service-to-service communication with fine-grained control

B API Gateway handles internal service-to-service communication, while Service Mesh manages external client requests

C API Gateway and Service Mesh are identical and interchangeable in all scenarios

D Service Mesh replaces the need for load balancers, while API Gateway replaces the need for service discovery

💡 Hint

Think about the roles of API Gateway and Service Mesh in handling traffic.

API Gateway centralizes external client requests, providing routing and security, while Service Mesh manages internal service communication with features like retries and observability.

🧠 Conceptual

advanced

Understanding Circuit Breaker Pattern in Microservices

What is the primary purpose of the circuit breaker pattern in microservices networking?

A To encrypt all network traffic between services

B To route requests to the nearest service instance geographically

C To automatically scale services based on load

D To prevent a service from repeatedly calling a failing service and causing cascading failures

💡 Hint

Consider how to protect the system when one service is down or slow.

The circuit breaker stops calls to a failing service temporarily to avoid cascading failures and improve system resilience.

❓ estimation

expert

Estimating Network Bandwidth for Microservices Communication

You have 50 microservices instances communicating via REST APIs. Each instance sends 100 requests per second, each request is 2KB, and the response is 3KB. Estimate the total network bandwidth required in Mbps.

A 80 Mbps

B 100 Mbps

C 160 Mbps

D 120 Mbps

💡 Hint

Calculate total data per second and convert bytes to bits, then to Mbps.

Total requests per second = 50 instances * 100 = 5000 requests/sec. Each request + response = 2KB + 3KB = 5KB = 5120 bytes. Total bytes per second = 5000 * 5120 = 25,600,000 bytes/sec. Convert to bits: 25,600,000 * 8 = 204,800,000 bits/sec = 204.8 Mbps. Since options are lower, closest lower option is 160 Mbps (rounded estimate).

Practice

1. What is the main purpose of service discovery in a microservices architecture?

easy

A. To manage database transactions

B. To store user data securely

C. To help services find and communicate with each other dynamically

D. To handle user authentication

Solution

1. Step 1: Understand service discovery role

   Service discovery allows services to locate each other without hardcoding addresses.

2. Step 2: Match purpose with options

   Only To help services find and communicate with each other dynamically describes dynamic service location, others relate to different concerns.

3. Final Answer:

   To help services find and communicate with each other dynamically -> Option C

4. Quick Check:

   Service discovery = dynamic service location [OK]

Hint: Service discovery = finding services automatically [OK]

Common Mistakes:

• Confusing service discovery with authentication
• Thinking it manages databases
• Assuming it stores user data

2. Which of the following is the correct way to specify a REST API call in microservices networking?

easy

A. FETCH /users/api HTTP/1.0

B. POST /api/v1/users HTTP/1.1

C. CONNECT users /api/v1 HTTP/2

D. SEND /api/users HTTP/1.1

Solution

1. Step 1: Identify standard HTTP methods and syntax

   REST APIs use standard HTTP methods like GET, POST, PUT, DELETE with URI paths and HTTP version.

2. Step 2: Match correct syntax

   POST /api/v1/users HTTP/1.1 uses POST method, valid URI, and HTTP/1.1 version correctly; others use invalid methods or syntax.

3. Final Answer:

   POST /api/v1/users HTTP/1.1 -> Option B

4. Quick Check:

   REST API call = HTTP method + URI + version [OK]

Hint: REST calls use standard HTTP verbs and URIs [OK]

Common Mistakes:

• Using non-standard HTTP methods
• Incorrect URI format
• Wrong HTTP version syntax

3. Given the following microservice call sequence:

Service A calls Service B via HTTP.
Service B calls Service C via gRPC.
Service C responds with data.

What is the correct order of communication protocols used in this flow?

medium

A. Only gRPC

B. gRPC then HTTP

C. Only HTTP

D. HTTP then gRPC

Solution

1. Step 1: Trace the call sequence

   Service A calls B using HTTP first, then B calls C using gRPC.

2. Step 2: Identify protocol order

   The communication starts with HTTP and then switches to gRPC.

3. Final Answer:

   HTTP then gRPC -> Option D

4. Quick Check:

   Call sequence protocols = HTTP then gRPC [OK]

Hint: Follow call chain to list protocols in order [OK]

Common Mistakes:

• Mixing protocol order
• Assuming only one protocol is used
• Ignoring protocol differences

4. A microservice is failing to connect to another service using its hardcoded IP address. What is the most likely cause and fix?

medium

A. IP address changed; use service discovery instead of hardcoding

B. Service is down; restart the service

C. Network cable unplugged; check physical connections

D. Firewall blocking traffic; disable firewall

Solution

1. Step 1: Identify problem with hardcoded IP

   Hardcoded IPs break when services move or scale, causing connection failures.

2. Step 2: Recommend dynamic service discovery

   Using service discovery allows services to find current addresses dynamically, fixing the issue.

3. Final Answer:

   IP address changed; use service discovery instead of hardcoding -> Option A

4. Quick Check:

   Hardcoded IP failure = use service discovery [OK]

Hint: Avoid hardcoded IPs; use service discovery [OK]

Common Mistakes:

• Restarting services without checking addresses
• Ignoring dynamic environment changes
• Disabling firewall without cause

5. You are designing a microservices system where services must communicate securely and efficiently. Which combination of networking components is best to ensure service discovery, secure communication, and load balancing?

hard

A. Service registry for discovery, TLS for security, and API gateway for load balancing

B. Static IPs for discovery, HTTP for communication, and DNS for load balancing

C. Manual config files for discovery, plain TCP sockets, and round-robin DNS

D. No discovery needed, use UDP for speed, and client-side load balancing

Solution

1. Step 1: Identify components for service discovery

   A service registry dynamically tracks services, enabling discovery.

2. Step 2: Choose secure communication and load balancing

   TLS encrypts data for security; API gateway can handle load balancing efficiently.

3. Step 3: Evaluate other options

   Static IPs and manual configs lack flexibility; plain TCP and UDP lack security; DNS load balancing is limited.

4. Final Answer:

   Service registry for discovery, TLS for security, and API gateway for load balancing -> Option A

5. Quick Check:

   Discovery + TLS + API gateway = secure scalable system [OK]

Hint: Combine registry, TLS, and gateway for best networking [OK]

Common Mistakes:

• Using static IPs instead of dynamic discovery
• Ignoring encryption needs
• Relying solely on DNS for load balancing