Question

You are responsible for the design of a communications switch that has to provide \(24 / 7\) availability, but which is not safety-critical. Giving reasons for your answer, suggest an architectural style that might be used for this system.

Short answer

Use microservices architecture for high availability and flexibility.

Step-by-step solution

Understand the Requirements

The switch must be available 24/7, which means it should be reliable and handle requests at any time without downtime. However, it is not safety-critical, so extreme measures like real-time constraints or redundancies necessary for life-critical systems may not be required.

Consider Architectural Styles

There are several architectural styles, but given the requirements of high availability and less criticality, styles like microservices, layered, or client-server could be considered. These styles support scalability, fault tolerance, and ease of maintenance.

Select the Appropriate Style

Microservices architecture would be a suitable choice as it allows components of the system to be distributed and independently deployed. This increases the system's reliability and availability since failures in one microservice do not necessarily take down the entire system.

Justify the Choice

Microservices architecture supports high availability due to its decentralized nature, allowing services to run independently. Moreover, it provides flexibility, as services can be deployed and scaled independently, crucial for non-stop operations.

Key concepts

Microservices

Microservices is a type of software architecture that breaks down a larger application into smaller, independently deployable services. Each service in a microservices architecture runs its own process and communicates with other services over a network, typically using lightweight protocols such as HTTP.
This setup allows for flexibility and robustness, which are essential in a system that requires continuous availability. One of the key benefits of microservices is their independence; if one service crashes or needs maintenance, the others can continue to operate without interruption. This is particularly beneficial for 24/7 operations, where downtime is not an option.
Additionally, microservices offer great scalability. Since each service can be scaled independently, it allows the system to handle varying loads efficiently by allocating more resources to high-demand services. This helps in maintaining the performance and availability of the system at all times. Another advantage is the ease of maintenance. Each microservice can be developed, deployed, and maintained independently, allowing teams to work autonomously, speeding up development cycles and incorporating new features or updates with minimal friction.

High Availability Systems

High availability systems are designed to ensure a high level of operational performance, usually by minimizing downtime. A system is typically considered highly available if it can operate continuously without failure for an extended period, such as 99.999% uptime in a year.
For systems that require 24/7 availability, high availability architectures use various strategies to achieve this goal. Key methods include fault tolerance, where systems are designed to work even if some components fail, and load balancing, where incoming requests are distributed across multiple servers to ensure no single server becomes overwhelmed.
Redundancy is another important concept in these systems. By having multiple instances of critical components, the system can seamlessly switch to a backup if the primary fails, thereby maintaining service continuity. In less safety-critical environments, like the communications switch designed in the exercise, high availability can be achieved without extreme redundancies, focusing instead on reliability and efficient recovery from failures.

Communications Switch Design

Designing a communications switch involves making choices that ensure it can handle all incoming and outgoing signals without interrupting service. Even though such a system is not safety-critical, its design must focus on maximizing uptime through careful architectural decisions.
With the adoption of a microservices architectural style, as suggested in the original solution, the communication switch can benefit from its modularity. Each functionality of the switch, such as routing or signal processing, can be handled by separate microservices, reinforcing system reliability as each function runs independently.
Furthermore, distributed design alleviates potential bottlenecks in network traffic management. If one microservice becomes unresponsive, others can continue to manage their respective tasks, preventing total system failure. The key to successful communications switch design lies in ensuring seamless interaction among microservices, which requires carefully planned communication protocols and data consistency measures, crucial for high availability.