Anti-patterns (distributed monolith, chatty services) in Microservices - Architecture Diagram

System Overview - Anti-patterns (distributed monolith, chatty services)

This system shows a microservices architecture suffering from two common anti-patterns: distributed monolith and chatty services. The services are tightly coupled and communicate excessively, causing high latency and poor scalability.

Key requirements include independent service deployment and efficient communication, which are violated here.

Architecture Diagram

User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  +-------------------+-------------------+
  |                   |                   |
Service A <---------> Service B <---------> Service C
  |                   |                   |
  +-------------------+-------------------+
          |                   |                   
          v                   v                   v
      Database A          Database B          Database C
          |                   |                   
          v                   v                   v
        Cache A             Cache B             Cache C

Components

User

user

End user initiating requests

Load Balancer

load_balancer

Distributes incoming requests to API Gateway instances

API Gateway

api_gateway

Routes requests to appropriate microservices

Service A

service

Handles part of business logic but depends heavily on Service B and C

Service B

service

Handles another part of business logic, tightly coupled with Service A and C

Service C

service

Handles additional business logic, communicates frequently with Service A and B

Database A

database

Stores data for Service A

Database B

database

Stores data for Service B

Database C

database

Stores data for Service C

Cache A

cache

Caches data for Service A to reduce DB load

Cache B

cache

Caches data for Service B to reduce DB load

Cache C

cache

Caches data for Service C to reduce DB load

Request Flow - 19 Hops

User → Load Balancer

Load Balancer → API Gateway

API Gateway → Service A

Service A → Service B

Service B → Service C

Service C → Cache C

Cache C → Service C

Service C → Database C

Service C → Service B

Service B → Cache B

Cache B → Service B

Service B → Database B

Service B → Service A

Service A → Cache A

Cache A → Service A

Service A → Database A

Service A → API Gateway

API Gateway → Load Balancer

Load Balancer → User

Failure Scenario

Component Fails:Service B

Impact:Service A and C calls to Service B fail, causing request failures and increased latency. The tightly coupled calls cause cascading failures.

Mitigation:Decouple services by using asynchronous communication or event-driven patterns. Implement circuit breakers to isolate failures and degrade gracefully.

Architecture Quiz - 3 Questions

Which anti-pattern is shown by the frequent synchronous calls between Service A, B, and C?

A CQRS pattern

B Event-driven architecture

C Chatty services

D Bulkhead isolation

Design Principle

This architecture highlights the importance of designing microservices to be loosely coupled and communicate efficiently. Avoiding chatty services and distributed monoliths improves scalability, reliability, and independent deployability.

Practice

1. Which of the following best describes a distributed monolith in microservices architecture?

easy

A. Services are fully independent and communicate rarely.

B. Services are tightly coupled and require coordinated deployment.

C. Services use asynchronous messaging to reduce latency.

D. Services are stateless and scale automatically.

Solution

1. Step 1: Understand distributed monolith characteristics

   A distributed monolith looks like microservices but behaves like a single app with tight coupling.

2. Step 2: Identify deployment and coupling issues

   Such services require coordinated deployment and cannot scale independently.

3. Final Answer:

   Services are tightly coupled and require coordinated deployment. -> Option B

4. Quick Check:

   Distributed monolith = tight coupling [OK]

Hint: Distributed monolith means tight coupling, not independence [OK]

Common Mistakes:

• Confusing distributed monolith with loosely coupled microservices
• Thinking distributed monolith scales independently
• Assuming distributed monolith uses asynchronous calls

2. Which syntax correctly describes a common symptom of chatty services in microservices communication?

easy

A. Service A uses event-driven messaging to notify Service B.

B. Service A calls Service B once per user request.

C. Service A calls Service B multiple times per user request.

D. Service A caches data to reduce calls to Service B.

Solution

1. Step 1: Define chatty services behavior

   Chatty services make many small calls between services per user request.

2. Step 2: Identify the correct syntax describing chatty calls

   Multiple calls per request indicate chatty communication.

3. Final Answer:

   Service A calls Service B multiple times per user request. -> Option C

4. Quick Check:

   Chatty services = many calls [OK]

Hint: Chatty means many calls, not just one [OK]

Common Mistakes:

• Choosing event-driven messaging as chatty behavior
• Assuming caching causes chatty services
• Thinking one call per request is chatty

3. Given a microservices system where Service A calls Service B 5 times and Service B calls Service C 3 times per user request, what is the total number of service calls triggered by one user request?

medium

A. 20

B. 15

C. 30

D. 8

Solution

1. Step 1: Calculate calls from Service A to B

   Service A calls Service B 5 times per request.

2. Step 2: Calculate calls from Service B to C triggered by A's calls

   Each of the 5 calls from A causes 3 calls from B to C, so 5 * 3 = 15 calls.

3. Step 3: Sum all calls

   Total calls = 5 (A->B) + 15 (B->C) = 20 calls.

4. Final Answer:

   20 -> Option A

5. Quick Check:

   5 + (5*3) = 20 [OK]

Hint: Multiply nested calls, then add all [OK]

Common Mistakes:

• Adding 5 + 3 instead of multiplying
• Ignoring nested calls from B to C
• Choosing sum as 18 instead of 20

4. You notice your microservices system has high latency due to many small synchronous calls between services. Which change would best fix this chatty service anti-pattern?

medium

A. Use asynchronous messaging or batch requests to reduce calls.

B. Combine tightly coupled services into a single service.

C. Add more synchronous calls to improve data freshness.

D. Increase the number of service instances to handle load.

Solution

1. Step 1: Identify chatty service problem

   Many small synchronous calls cause latency and network overhead.

2. Step 2: Choose solution to reduce call frequency

   Using asynchronous messaging or batching reduces calls and latency.

3. Final Answer:

   Use asynchronous messaging or batch requests to reduce calls. -> Option A

4. Quick Check:

   Reduce calls with async or batching [OK]

Hint: Reduce calls by batching or async messaging [OK]

Common Mistakes:

• Combining services creates distributed monolith
• Adding more sync calls worsens latency
• Scaling instances doesn't reduce call count

5. A company has a microservices system suffering from both distributed monolith and chatty services anti-patterns. Which combined approach best improves scalability and deployment independence?

hard

A. Merge all services into one large application to simplify deployment.

B. Increase hardware resources and add load balancers to handle traffic.

C. Use synchronous REST calls extensively to keep services tightly connected.

D. Refactor services to reduce dependencies and use asynchronous communication.

Solution

1. Step 1: Address distributed monolith by reducing dependencies

   Refactoring services to be loosely coupled allows independent deployment and scaling.

2. Step 2: Fix chatty services by adopting asynchronous communication

   Using async messaging reduces frequent synchronous calls and network overhead.

3. Step 3: Combine both improvements for better scalability and independence

   This combined approach solves both anti-patterns effectively.

4. Final Answer:

   Refactor services to reduce dependencies and use asynchronous communication. -> Option D

5. Quick Check:

   Loose coupling + async = scalable microservices [OK]

Hint: Loose coupling + async communication fixes both issues [OK]

Common Mistakes:

• Merging services worsens distributed monolith
• Adding hardware doesn't fix design flaws
• Using more sync calls increases chatty problems