Services and networking in Microservices - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a microservice in the context of services and networking?

A microservice is a small, independent service that performs a specific business function and communicates with other services over a network.

beginner

Why do microservices communicate over a network instead of sharing memory?

Because microservices run independently on different machines or containers, they use network communication to stay loosely coupled and scalable.

intermediate

What is an API Gateway in microservices networking?

An API Gateway is a server that acts as a single entry point for clients to access multiple microservices, handling routing, security, and load balancing.

intermediate

Explain service discovery in microservices networking.

Service discovery is the process where microservices find the network locations of other services dynamically, often using a registry to keep track of available services.

intermediate

What role does load balancing play in microservices networking?

Load balancing distributes incoming network traffic evenly across multiple instances of a microservice to improve reliability and performance.

Which component acts as a single entry point for client requests in a microservices architecture?

A API Gateway

B Service Registry

C Database

D Load Balancer

The API Gateway handles client requests and routes them to the appropriate microservices.

What is the main purpose of service discovery in microservices?

A To encrypt communication

B To store user data

C To find the network location of services dynamically

D To balance network traffic

Service discovery helps microservices locate each other dynamically on the network.

Why do microservices communicate over a network instead of sharing memory?

A Because sharing memory is faster

B Because they run independently and may be on different machines

C Because network communication is less secure

D Because they use the same database

Microservices are independent and distributed, so they communicate over the network.

What does load balancing do in a microservices system?

A Stores service configurations

B Encrypts data in transit

C Monitors service health

D Distributes traffic evenly across service instances

Load balancing spreads incoming requests to multiple service instances to improve performance.

Which of the following is NOT a typical responsibility of an API Gateway?

A Service discovery

B Load balancing

C Routing requests

D Authentication

Service discovery is usually handled by a separate registry, not the API Gateway.

Describe how microservices communicate and the role of networking components like API Gateway and service discovery.

Think about how independent services find and talk to each other.

Explain why load balancing is important in a microservices architecture and how it improves system reliability.

Imagine many people trying to enter a store at once.

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