How do you choose the right protocol for your microservices?

In my experience its totally dependends on use case, Synchronous communication involves direct request-response interaction between microservices. Use case like CRUD operation, authentication and authorization. Asynchronous communication involves decoupled interaction where source service broadcast an event and continues its work without waiting for immediate response from the destination service. For handing long running task , background processes and scenario where services can function parallelly to complete a task. Use case like ecommerce order processing, social media update (post).

For me all depends upon your use case to choose a protocol. Advantage having a synchronous communication is it;s simplicity quick response. The downside is synchronous calls are tight coupled and you next task is on hold till the response is received. Some common use case are check out, adding item to cart, or buy now option we use in eCommerce application. Asynchronous communication is popular due to flexibility and number of advantages over synchronous. Developer prefer due to it's loosely coupled and non blocking nature. One of the major disadvantage of asynchronous communication is delayed response and implementing complexities. Some of the real world example email notification service large image uploading and thumb nail creation.

Choosing between synchronous and async communication in microservices is a crucial architectural decision. Synchronous communication offers simplicity and speed but increases coupling and potential latency issues. On the other hand, asynchronous communication enhances scalability and resilience at the cost of added complexity and potential inconsistencies. The choice should align with your business logic, performance, and reliability requirements, ensuring the architecture supports your system's long-term goals. Picture a relay race versus a marathon. In a relay, runners depend on precise handoffs (synchro), but in a marathon, each runner follows their own pace (async). Choose the race that matches your software's stamina and strategy.

For internal systems or outgoing messaging always prefer event driven, loosely coupled services. This provides the ability to more easily deploy, scale, and evolve service architecture.

- If your operations require immediate feedback and are relatively quick, synchronous protocols might be more appropriate. - For operations that are long-running or do not require immediate response, asynchronous communication can provide better performance and resource usage.

When choosing a protocol for synchronous communication, REST and gRPC are top contenders. REST, based on HTTP, is user-friendly, widely supported, and human-readable, ideal for straightforward integrations. However, it can be verbose and lacks type safety. gRPC offers speed, efficiency, and strong type safety through HTTP/2 and protocol buffers but has a steeper learning curve and limited browser support. Your choice should align with your data's size, format, and compatibility needs. REST is like a universal translator—clear but wordy. gRPC is a fast interpreter—precise but demanding. Pick the one that best fits your system’s needs.

- Choose REST for public-facing APIs or when ease of use and compatibility are paramount. - Opt for gRPC for internal service communication, especially in performance-sensitive environments.

REST is typically used for its ease of use and compatibility with the web, fitting for stateless interactions and widely accessible APIs. gRPC is chosen for its performance efficiency in server-to-server communications, particularly for internal microservices that require fast, bidirectional communication, like real-time data syncing in our CMS

I have found gRPC faster and easier. But, as said it is still not supported by many browser. But definitely very good for microservices.

Once more, the choice between REST and gRPC can be made based on the project's objectives, use cases, accessibility, decision regarding synchronous or asynchronous communication, whether the project will be a public API, web services, and whether or not simplicity and compatibility are crucial. I would like to believe gRPC will be most suited in cases where the project is an internal tool that will require type-safe, tight contract compliance, involves working with streams and data in bits and REST if not. Not ignoring the fact that REST is easier to tweak during implementation, has a broader community support, and is backwards-compatible with a wider range of browsers. It is best to survey the use-cases then make decisions as appropriate

Choosing between message brokers and event streams depends on data volume, processing needs, and consumer patterns. Message brokers (e.g., RabbitMQ) are versatile for various messaging patterns and ensure delivery with options for multiple consumers, making them ideal for guaranteed, order-specific processing. Conversely, event streams (e.g., Apache Kafka) excel at handling large volumes of real-time data and support event processing with low latency, supporting independent stream reading by multiple consumers. While message brokers provide straightforward integration and management, event streams are better for advanced, large-scale analytics requirements. Both often complement each other to maximize benefits in different scenarios.

Use message brokers for scenarios requiring complex routing, decoupling of services, and guaranteed delivery. Choose event streams for scenarios requiring high throughput, durable event logging, and real-time processing.

Message brokers are key in scenarios where reliable delivery of individual messages is critical, like transaction processing. For our CMS, brokers manage task queues for content moderation. Event streams are advantageous for scenarios that require processing streams of events or real-time data analysis, as we use for tracking user engagement within the CMS.

Another important distinction not mentioned is that message brokers delete messages once they are received by a consumer while event streams like Kafka are immutable meaning they retain records of events. This allows events to be replayed when necessary.

You should also think about server side events (one way) or web-sockets (two way) when dealing with asynchronous communication on front end. Sometimes, a user just needs to be acknowledged that their request was received but not yet processed. Status of their request can be notified later via notifications, a status bar, etc. in real time via notifications from the server. This helps to solve client side delays if your backend cannot promise reasonable response latency due to any underlying problem e.g. legacy systems or heavy processing.

When making decisions about communication protocols or architectural choices, consider not just the technical aspects but also your team's expertise and the project's future evolution. The best solution isn't always the most advanced; it’s the one that aligns with your team’s skills and your system's growth trajectory. Always plan for the long-term impact of your choices. Imagine building a bridge. The most complex design might impress, but if your crew isn't familiar with the materials, it could collapse. Choose tools and methods that ensure your project’s success, now and in the future.

Compatibility and Ecosystem: Consider the compatibility of the protocol with your current technology stack and its support within your ecosystem. Developer Experience: Some protocols may require more learning or specialized knowledge. Consider the impact on developer productivity. Performance Requirements: Assess the performance implications of each protocol in terms of latency, throughput, and resource utilization. Scalability and Flexibility: Consider how well the protocol supports scaling and evolving your architecture over time. Security Requirements: Evaluate the security features and implications of each protocol, especially for public-facing APIs.

Assess latency implications for real-time systems, ensure scalability for future growth, minimize complexity for easier maintenance, check ecosystem support for robust development, and prioritize security for data integrity and privacy. These considerations consistently inform the architectural decisions for our CMS platform.

When I was working for an App, JavaScript or Typescript did not have support for gRPC. But there were some workarounds, though not very efficient. We ended up with REST.

Selecting the proper communication protocol for microservices involves assessing real-time interactions, performance metrics like latency and throughput, and data exchange requirements (synchronous or asynchronous, one-to-one, or one-to-many). Options include HTTP/REST for simplicity, gRPC for high-performance and efficient data exchanges, AMQP for reliable messaging, and MQTT for IoT-focused communications. The decision should consider scalability, fault tolerance, security (such as SSL/TLS for encryption), community support, and tools. Prototyping different protocols can help determine the best fit, often leading to a hybrid approach that uses different protocols for varying system needs.