Monolithic Application vs Microservices

Monolithic Application

• A monolithic application is a single-tiered software application that combines the user interface and data access code into a single program from a single platform.
• It is self-contained and independent from other computing applications.
• The application is responsible for performing every step needed to complete a particular function.

Microservices

• Microservices are small, independent, and loosely coupled.
• Each service is a separate codebase, which can be managed by a small development team.
• Services can be deployed independently, and a team can update an existing service without rebuilding and redeploying the entire application.
• Services are responsible for persisting their own data or external state.
• Services communicate with each other by using well-defined APIs.
• Internal implementation details of each service are hidden from other services.
• Microservices support polyglot programming, allowing services to use different technology stacks, libraries, or frameworks.

From Monolithic to Microservices

• Example: Hospital OPD (OutPatient Department)
• Each department can be a separate microservice, communicating with each other using APIs.

Benefits of Microservices Architecture

Faster Deployments

• Microservices architecture allows for faster development and deployments since it simplifies the design.
• Each module is easily built, tested, and deployed independently, giving businesses increased agility and faster time to market.

Scalability

• Microservices architecture offers ease in scalability since the modules work independently and each has bounded context.
• The design is far more simple, allowing fast adding of new features.

Guaranteed up-time

• With the right microservices architecture, it’s almost impossible for the whole system to go down.
• Each microservice is built, deployed, and managed independently, isolating runtime failures.

No Vendor Lock

• Microservices architecture and principles are based on open standards and backed up heavily by the open-source community.
• Almost all commercial microservices platforms follow these open standards, making it easy to migrate from them if needed.

Resilience & Robustness

• With microservices architecture, platforms are far more resilient and robust.
• Kubernetes or OpenShift Container platforms are monitoring and self-healing whenever the system is affected.

Dynamic Talent Pool

• With microservices, it’s easier to onboard new team members as well as hire software engineers with different coding backgrounds.

Challenges in Microservices

• Complexity: A microservices application has more moving parts than the equivalent monolithic application.
• Development and testing: Writing a small service that relies on other dependent services requires a different approach than writing a traditional monolithic or layered application.
• Network congestion and latency: The use of many small, granular services can result in more interservice communication.
• Versioning: Also known as Asynchronous communication, services push messages to a message broker that other services subscribe to.

API Gateway

• API Gateway is a fully managed service that makes it easy for developers to create, publish, maintain, monitor, and secure APIs at any scale.
• APIs act as the "front door" for applications to access data, business logic, or functionality from backend services.

Service Discovery

• In a modern, cloud-based microservices application, service instances have dynamically assigned network locations.
• Clients need to use a more elaborate service discovery mechanism.
• Solution: Using a Service Registry to maintain a database of available service instances.

Service Registry

• Service registry is a database of available service instances.
• It assures high availability and keeps refreshing the network location of service instances.
• Example: Netflix Eureka provides a REST API to register and query service instances.