API key management in Microservices - Architecture Diagram

System Overview - API key management

This system manages API keys for users and services. It securely generates, stores, validates, and revokes API keys to control access to APIs. The system must be scalable, secure, and provide fast validation for incoming requests.

Architecture Diagram

User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  +-------------------+
  |                   |
  v                   v
API Key Service     Business Service
  |                   |
  v                   v
Database (API Keys)  Database (Business Data)
  |
  v
Cache (API Keys)

Components

User

client

Sends API requests with API keys

Load Balancer

load_balancer

Distributes incoming requests evenly to API Gateway instances

API Gateway

api_gateway

Receives requests, validates API keys, routes to services

API Key Service

service

Generates, stores, validates, and revokes API keys

Business Service

service

Handles business logic after API key validation

Database (API Keys)

database

Stores API key data securely

Cache (API Keys)

cache

Caches API key validation results for fast lookup

Database (Business Data)

database

Stores business-related data

Request Flow - 15 Hops

User → Load Balancer

Load Balancer → API Gateway

API Gateway → Cache (API Keys)

Cache (API Keys) → API Gateway

API Gateway → API Key Service

API Key Service → Database (API Keys)

Database (API Keys) → API Key Service

API Key Service → Cache (API Keys)

API Key Service → API Gateway

API Gateway → Business Service

Business Service → Database (Business Data)

Database (Business Data) → Business Service

Business Service → API Gateway

API Gateway → Load Balancer

Load Balancer → User

Failure Scenario

Component Fails:Cache (API Keys)

Impact:API Gateway cannot quickly validate API keys from cache, causing increased latency due to database queries.

Mitigation:System falls back to API Key Service querying the database directly. Cache is rebuilt asynchronously. This ensures correctness but with slower response times.

Architecture Quiz - 3 Questions

Which component is responsible for distributing incoming user requests evenly?

A Load Balancer

B API Gateway

C API Key Service

D Cache

Design Principle

This architecture uses caching to speed up API key validation and separates concerns by having a dedicated API Key Service. It ensures scalability by load balancing and maintains security by centralizing key management.

Practice

1. What is the primary purpose of API key management in microservices?

easy

A. To generate random data for APIs

B. To speed up API response times

C. To store user passwords securely

D. To control and monitor access to APIs

Solution

1. Step 1: Understand API key management role

   API key management is about controlling who can use APIs and tracking their usage.

2. Step 2: Identify the main goal

   The main goal is to secure APIs by controlling and monitoring access, not speeding up or storing passwords.

3. Final Answer:

   To control and monitor access to APIs -> Option D

4. Quick Check:

   API key management = Access control [OK]

Hint: API keys control who uses your API [OK]

Common Mistakes:

• Confusing API keys with password storage
• Thinking API keys improve speed
• Assuming API keys generate data

2. Which of the following is the correct way to represent an API key in a request header?

easy

A. Auth-Key: <API_KEY>

B. Authorization: Bearer <API_KEY>

C. API-Key: <API_KEY>

D. Key: <API_KEY>

Solution

1. Step 1: Review common API key header formats

   API keys are often sent in headers named API-Key or similar, but Authorization: Bearer is usually for tokens, not API keys.

2. Step 2: Identify the standard header for API keys

   API-Key is the widely accepted header for API keys, making API-Key: <API_KEY> correct.

3. Final Answer:

   API-Key: <API_KEY> -> Option C

4. Quick Check:

   API key header = API-Key [OK]

Hint: API keys use 'API-Key' header, not 'Authorization: Bearer' [OK]

Common Mistakes:

• Using 'Authorization: Bearer' for API keys
• Confusing header names
• Omitting the key value

3. Given this pseudocode for API key validation:

function validateKey(request) {
  key = request.headers['API-Key']
  if key is null or key not in validKeys:
    return 'Access Denied'
  else:
    return 'Access Granted'
}

What will be the output if the request has no 'API-Key' header?

medium

A. Access Denied

B. Error: Missing header

C. Access Granted

D. Access Pending

Solution

1. Step 1: Check header presence condition

   The code checks if the key is null or not in validKeys. If the header is missing, key is null.

2. Step 2: Determine the return value for missing key

   Since key is null, the condition is true, so the function returns 'Access Denied'.

3. Final Answer:

   Access Denied -> Option A

4. Quick Check:

   Missing key = Access Denied [OK]

Hint: No API-Key header means deny access [OK]

Common Mistakes:

• Assuming missing key grants access
• Expecting an error instead of denial
• Confusing 'null' with empty string

4. A developer wrote this code snippet to revoke an API key:

function revokeKey(key) {
  if key in activeKeys:
    activeKeys.remove(key)
  else:
    print('Key not found')
}

But the key is still accepted after revocation. What is the likely issue?

medium

A. The remove method does not delete keys properly

B. The key is not removed from the validKeys list used for validation

C. The function does not print 'Key revoked' message

D. The key is being re-added automatically elsewhere

Solution

1. Step 1: Understand key revocation logic

   The function removes the key from activeKeys, but validation likely checks validKeys.

2. Step 2: Identify mismatch in key storage

   If validation uses validKeys and revoke removes from activeKeys, the key remains valid.

3. Final Answer:

   The key is not removed from the validKeys list used for validation -> Option B

4. Quick Check:

   Revocation must remove key from validation list [OK]

Hint: Revoking must remove key from validation store [OK]

Common Mistakes:

• Removing key from wrong list
• Assuming print messages affect logic
• Ignoring other code re-adding keys

5. You need to design an API key management system for a microservices platform that supports millions of users. Which approach best balances security, scalability, and ease of revocation?

hard

A. Store API keys in a centralized database with caching and use short-lived keys with rotation

B. Embed API keys directly in client apps without server validation

C. Use a single global API key for all users to simplify management

D. Store API keys only in memory on each microservice without persistence

Solution

1. Step 1: Evaluate security and scalability needs

   Millions of users require scalable storage and fast validation. Centralized DB with caching supports this.

2. Step 2: Consider revocation and key rotation

   Short-lived keys with rotation improve security and allow easy revocation without downtime.

3. Step 3: Eliminate insecure or unscalable options

   Embedding keys in clients or using a single key is insecure; in-memory only storage lacks persistence and scalability.

4. Final Answer:

   Store API keys in a centralized database with caching and use short-lived keys with rotation -> Option A

5. Quick Check:

   Central DB + caching + rotation = secure & scalable [OK]

Hint: Use central DB with caching and rotate keys regularly [OK]

Common Mistakes:

• Using single global key for all users
• Not persisting keys for revocation
• Embedding keys insecurely in clients