Backend for Frontend (BFF) pattern in Microservices - Architecture Diagram

System Overview - Backend for Frontend (BFF) pattern

The Backend for Frontend (BFF) pattern creates a dedicated backend service for each user interface or client type, such as web or mobile. This helps tailor APIs to the specific needs of each frontend, improving performance and simplifying frontend logic.

Key requirements include handling different data formats, aggregating data from multiple microservices, and reducing over-fetching or under-fetching of data.

Architecture Diagram

User (Web)   User (Mobile)
   |             |
   v             v
+--------+   +--------+
|  BFF   |   |  BFF   |
| Web BFF|   |Mobile BFF|
+--------+   +--------+
    |            |
    v            v
+---------------------+
|    API Gateway      |
+---------------------+
    |       |       |
    v       v       v
+-------+ +-------+ +-------+
|Service| |Service| |Service|
|   A   | |   B   | |   C   |
+-------+ +-------+ +-------+
    |        |        |
    v        v        v
+--------------------------------+
|          Databases              |
+--------------------------------+

Components

User (Web)

client

Web browser user interface

User (Mobile)

client

Mobile app user interface

Web BFF

service

Backend tailored for web frontend, aggregates and formats data

Mobile BFF

service

Backend tailored for mobile frontend, optimizes data for mobile usage

API Gateway

api_gateway

Routes requests from BFFs to appropriate microservices

Service A

microservice

Handles specific business logic and data

Service B

microservice

Handles specific business logic and data

Service C

microservice

Handles specific business logic and data

Databases

database

Stores persistent data for microservices

Request Flow - 10 Hops

User (Web) → Web BFF

Web BFF → API Gateway

API Gateway → Service A

API Gateway → Service B

Service A → Databases

Service B → Databases

Service A → API Gateway

Service B → API Gateway

API Gateway → Web BFF

Web BFF → User (Web)

Failure Scenario

Component Fails:Web BFF

Impact:Web users cannot get tailored data; frontend may fail or show errors

Mitigation:Implement redundancy with multiple Web BFF instances behind a load balancer; fallback to generic API Gateway if needed

Architecture Quiz - 3 Questions

What is the main purpose of the Backend for Frontend (BFF) service?

A To store user data persistently

B To replace the API Gateway entirely

C To tailor backend responses specifically for each frontend client

D To act as a database cache

Design Principle

The BFF pattern improves frontend performance and developer experience by creating backend services tailored to each client type. This reduces unnecessary data transfer and complexity on the frontend, while keeping microservices focused on business logic.

Practice

1. What is the main purpose of the Backend for Frontend (BFF) pattern in microservices architecture?

easy

A. To directly connect frontends to databases without backend logic

B. To replace all microservices with a single monolithic backend

C. To create a backend service tailored specifically for each frontend client

D. To merge all frontend code into one application

Solution

1. Step 1: Understand BFF role

   BFF acts as a specialized backend that serves the needs of a specific frontend, like mobile or web.

2. Step 2: Compare with other options

   Options B, C, and D do not describe BFF but other unrelated or incorrect architectures.

3. Final Answer:

   To create a backend service tailored specifically for each frontend client -> Option C

4. Quick Check:

   BFF = tailored backend for frontend [OK]

Hint: BFF means backend made just for one frontend [OK]

Common Mistakes:

• Thinking BFF replaces microservices
• Confusing BFF with frontend code merging
• Assuming BFF connects frontend directly to database

2. Which of the following is the correct way to describe the BFF pattern's interaction with microservices?

easy

A. BFF aggregates data from multiple microservices for frontend use

B. BFF sends frontend code to microservices

C. BFF replaces microservices with a single service

D. BFF directly modifies microservices' databases

Solution

1. Step 1: Identify BFF's role with microservices

   BFF collects and combines data from various microservices to serve frontend needs efficiently.

2. Step 2: Eliminate incorrect options

   Options A, B, and C describe incorrect or impossible interactions.

3. Final Answer:

   BFF aggregates data from multiple microservices for frontend use -> Option A

4. Quick Check:

   BFF aggregates microservices data [OK]

Hint: BFF collects data from many microservices [OK]

Common Mistakes:

• Assuming BFF changes microservices' databases
• Thinking BFF replaces microservices
• Believing BFF sends frontend code to backend

3. Consider a BFF that calls two microservices: User Service and Order Service. If User Service returns {"name": "Alice"} and Order Service returns {"orders": 3}, what will the BFF likely return to the frontend?

medium

A. {"name": "Alice"}

B. {"orders": 3}

C. {"name": "Alice", "orders": 3}

D. {"user": {"name": "Alice"}, "order": {"orders": 3}}

Solution

1. Step 1: Understand BFF data aggregation

   BFF combines data from multiple microservices into a single response for frontend simplicity.

2. Step 2: Analyze the combined response

   The best practice is to namespace responses to avoid key collisions, resulting in {"user": {"name": "Alice"}, "order": {"orders": 3}}.

3. Final Answer:

   {"user": {"name": "Alice"}, "order": {"orders": 3}} -> Option D

4. Quick Check:

   BFF namespaces microservices data to avoid conflicts [OK]

Hint: BFF namespaces microservices responses [OK]

Common Mistakes:

• Merging keys without namespaces causing conflicts
• Returning only one microservice's data
• Confusing keys or data structure

4. A developer wrote a BFF that calls multiple microservices but the frontend receives slow responses. What is the most likely cause?

medium

A. BFF is making synchronous calls to microservices one after another

B. BFF caches all responses aggressively

C. BFF uses asynchronous calls to microservices

D. BFF compresses responses before sending

Solution

1. Step 1: Identify cause of slow response

   Making synchronous calls one after another causes delays as each waits for the previous to finish.

2. Step 2: Evaluate other options

   Caching and compression usually improve speed; asynchronous calls also improve speed.

3. Final Answer:

   BFF is making synchronous calls to microservices one after another -> Option A

4. Quick Check:

   Synchronous calls cause slow BFF responses [OK]

Hint: Synchronous calls slow down BFF responses [OK]

Common Mistakes:

• Assuming caching slows down responses
• Confusing async with sync calls
• Ignoring network latency impact

5. You are designing a BFF for a mobile app and a web app. The mobile app needs minimal data for fast loading, while the web app needs detailed data. How should you design your BFFs?

hard

A. Use a single BFF that returns all data to both frontends

B. Create separate BFFs for mobile and web, each tailoring data to its frontend

C. Let frontends call microservices directly to get needed data

D. Create one BFF that returns minimal data for both frontends

Solution

1. Step 1: Understand frontend needs

   Mobile requires less data for speed; web requires more detailed data.

2. Step 2: Apply BFF pattern best practice

   Separate BFFs allow tailoring responses to each frontend's needs, improving performance and simplicity.

3. Final Answer:

   Create separate BFFs for mobile and web, each tailoring data to its frontend -> Option B

4. Quick Check:

   Separate BFFs tailor data per frontend [OK]

Hint: Use separate BFFs for different frontend needs [OK]

Common Mistakes:

• Using one BFF for all frontends ignoring needs
• Letting frontends call microservices directly
• Returning minimal data to all frontends