Synchronous execution requires parts or components to work simultaneously in real time, while asynchronous communication requires no one to wait for a response.
Software architects and developers need to understand the difference between synchronous and asynchronous communication and how they apply to program execution and system design.
What is synchronous and asynchronous communication?
In synchronous communication, multiple parties are constantly listening and acting on feedback from others. One way to visualize the concept of synchronous communication is to imagine a real-time live chat system designed to support a retailer’s customers. Support specialists quickly exchange messages with customers to help them track orders, report missing deliveries, or inquire about a product.
until it receives a call, response, value, or other data transfer. For example, synchronous execution occurs during online shopping. The user decides to buy a product and the system generates a query to determine if the product is in stock. The application waits for a response before starting the payment process. This unified design avoids delays between inventory and sales.
In contrast, asynchronous communication allows code to continue executing after a call or response is made. Asynchronous communication is particularly useful for reporting and alerting, such as manufacturing applications that monitor industrial furnace temperatures, continuously transmit status updates, and automatically send alerts.
This type of application will never stop and wait for a response before taking the next action. Instead, communication alone will trigger an action from another employee or another application. For example, an application could send temperature updates asynchronously throughout the day and trigger a troubleshooting sequence whenever the temperature rises or falls below an acceptable level.
Advantages and disadvantages of synchronous communication compared to asynchronous communication:
Both synchronous and asynchronous methods have potential advantages and disadvantages, but the method you choose depends on the purpose of your application. Synchronous communication is designed to be simpler, but there is a risk of error propagation between services. To mitigate this risk, architects should implement sophisticated service discovery and application load balancing on microservices.
Asynchronous communication, on the other hand, trades architectural simplicity and data consistency for resiliency and scalability. Asynchronous designs generally provide better error control than synchronous configurations. Consider starting with a synchronous system to maximize scalability, and move to asynchronous communication as your microservices architecture evolves. Best practices for synchronous and asynchronous communication:
Consistency around communication between services is one of the challenges of distributed architectures like microservices. There are several approaches to address this challenge.
Communication between services in a microservices architecture can be:
Decentralized and synchronous:
choreographed and asynchronous; or
coordinated and synchronous/asynchronous. Consider synchronous and asynchronous communication:
A number of issues can arise with both synchronous and asynchronous communication processes, all of which can have a significant impact on the performance of an application system. These challenges are almost always exaggerated when applied to distributed systems, especially with respect to concurrency, workflow, and component tracking.
Airsickness:
Clock skew is a situation in which the digital components involved receive time indications at different intervals, which has a significant impact on the performance of the synchronous system. This can especially cause problems in densely designed systems containing a large number of components.
Data storage and integrity:
Cloud data storage, especially cloud backup for on-premises systems, can place primary data and backup data in different locations. Remote synchronous replication indicates that read and write operations occur in time with primary and backup data stores. Communication monitoring:
In most monolithic application architectures, statements about system behavior are relatively explicit as part of application design. However, when the underlying architecture includes distributed services, it becomes more difficult to monitor the flow of communication.
