What are the most effective patterns for microservices communication in web applications?

1 Synchronous vs. Asynchronous

One of the first decisions you need to make when designing microservices communication is whether to use synchronous or asynchronous methods. Synchronous communication means that the caller waits for the response from the callee, while asynchronous communication means that the caller does not wait and can continue with other tasks. Synchronous communication is simpler to implement and understand, but it can also create dependencies, bottlenecks, and timeouts. Asynchronous communication is more scalable and resilient, but it can also introduce complexity, inconsistency, and uncertainty. The best choice depends on your business requirements, such as the need for real-time feedback, data accuracy, or user experience.

2 REST vs. gRPC

Another decision you need to make is whether to use REST or gRPC as the protocol for microservices communication. REST stands for Representational State Transfer, and it is a widely used standard for web APIs that uses HTTP methods, URLs, and JSON or XML formats. gRPC stands for gRPC Remote Procedure Calls, and it is a newer framework that uses HTTP/2, binary encoding, and protocol buffers. REST is more flexible, interoperable, and human-readable, but it can also be verbose, inefficient, and inconsistent. gRPC is more efficient, performant, and consistent, but it can also be less compatible, harder to debug, and more complex. The best choice depends on your technical requirements, such as the data size, network speed, or platform diversity.

3 Message Broker

A message broker is a software component that mediates the communication between microservices by using a publish-subscribe model. In this model, the microservices that produce messages (publishers) do not send them directly to the microservices that consume them (subscribers), but rather to a message broker that handles the routing, delivery, and persistence of the messages. A message broker can help you achieve asynchronous communication, decoupling, scalability, and reliability. However, a message broker can also introduce overhead, latency, and complexity. Some of the popular message brokers for microservices are Kafka, RabbitMQ, and ActiveMQ.

4 API Gateway

An API gateway is a software component that acts as a single entry point for all the external requests to your web application. An API gateway can help you simplify the communication between the clients and the microservices by providing features such as authentication, authorization, routing, load balancing, caching, logging, and monitoring. An API gateway can help you improve the security, performance, and usability of your web application. However, an API gateway can also become a single point of failure, a performance bottleneck, and a maintenance challenge. Some of the popular API gateways for microservices are Kong, Tyk, and AWS API Gateway.

5 Service Discovery

Service discovery is a process that enables the microservices to find and communicate with each other dynamically, without hard-coding their locations or configurations. Service discovery can help you cope with the changes in the network topology, the number of instances, and the availability of the microservices. Service discovery can be implemented using two approaches: client-side or server-side. Client-side service discovery means that the microservices query a service registry that maintains the information about the other microservices, and then use a load balancer to select the best instance. Server-side service discovery means that the microservices send their requests to a router that queries the service registry and forwards the requests to the appropriate instance. Some of the popular service discovery tools for microservices are Consul, Eureka, and ZooKeeper.

6 Circuit Breaker

A circuit breaker is a software component that monitors the communication between the microservices and detects failures or delays. A circuit breaker can help you prevent cascading failures, improve resilience, and optimize resource utilization. A circuit breaker works by using three states: closed, open, and half-open. Closed means that the communication is normal and the requests are sent to the callee. Open means that the communication is broken and the requests are rejected or redirected to a fallback mechanism. Half-open means that the communication is being tested and some requests are sent to the callee to check if it has recovered. Some of the popular circuit breaker libraries for microservices are Hystrix, Resilience4j, and Polly.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?