Article 10: Securing Microservices with JWT

1. Objective

Implement authentication and authorization across microservices using JWT.

2. Key Concepts

• Authentication vs Authorization
• JWT (JSON Web Token)
• Gateway-level security

3. Why Security at Gateway

• Single entry point
• Avoid duplication
• Centralized control

4. JWT Flow

Client -> Auth Service -> JWT -> API Gateway -> Microservices

5. Hands-On: JWT Validation at Gateway

Dependencies:

• spring-boot-starter-security

Security config:

@EnableWebFluxSecurity
public class SecurityConfig {

    @Bean
    public SecurityWebFilterChain filterChain(ServerHttpSecurity http) {
        http
            .csrf().disable()
            .authorizeExchange()
            .pathMatchers("/auth/**").permitAll()
            .anyExchange().authenticated()
            .and()
            .oauth2ResourceServer()
            .jwt();
        return http.build();
    }
}

6. Token Validation

• Validate signature
• Validate expiry
• Validate roles

7. Common Mistakes

• Securing every service separately
• Ignoring token expiry
• Hardcoding secrets

8. Interview Notes

• JWT is stateless
• Gateway security simplifies architecture

9. Summary

JWT-based security is standard for microservices.

10. What’s Next

Handle data consistency and transactions.