How do you evaluate the trade-offs between reusing existing microservices and creating new ones?

Reusing microservices means leveraging existing, independently deployable services in new applications or contexts rather than building new ones from scratch.

It depends on some factors such as business needs, delivery time and technical capabilities. As in some cases reusing existing microservices will be the ideal approach to maintain the stability and reliability and when the reuse satisfy the business needs and does not violate the followed technical outlines. While at some other cases creating new microservices will add competitive edge regarding the business satisfaction by leverage higher performance features and increase the reliability and the maintainability of the solution.

Deciding to reuse or create new microservices hinges on assessing core functionalities against specific business needs and technical compatibility. Reuse when a microservice aligns well with business goals, offers stable, widely used functions, and meets quality standards within your tech ecosystem. This approach maximizes efficiency and maintains system integrity.

Functionality matches requirements closely Service is stable and well-maintained Reuse saves significant development time Consistency across applications is desired

at the end of the day, conducting short term cost-benefit analysis and long-term implications is preferred way for making choice whether to reuse existing or building new one

Reuse is often preferable when an existing microservice meets the new functionality with minimal modifications, ensuring consistency and reducing the risk of introducing new bugs. However, it's important to assess whether the microservice can scale to meet new demands and whether its reuse might introduce unnecessary dependencies or complexity.

New microservices should be created when a distinct, well-defined domain or functionality is identified that doesn't align well with existing services, or when there's a need for independent scaling, deployment, or lifecycle management. Additionally, if reusing an existing microservice would lead to tight coupling, increased complexity, or hindered agility due to overloading it with responsibilities, creating a new microservice is the better option to maintain a clean, modular architecture.

Existing services don't meet specific needs New functionality is unique to the project Existing services have poor performance or reliability Decoupling from legacy systems is necessary

Ensure proper documentation and versioning Use well-defined APIs and contracts Implement robust testing and monitoring Consider using service meshes for management

Define clear boundaries and responsibilities Use domain-driven design principles Implement CI/CD pipelines from the start Design for scalability and resilience

Such trade-offs, whether in favour of reuse as opposed to new development, have to consider issues of complexity of services, maintainability, and business alignment to need. While reuse saves time and effort that would be spent on the development of services, it may introduce dependencies that complicate maintenance or restrict flexibility. On one hand, it could result in the development of new microservices with a much better fit for certain requirements. However, it would most probably further increase labor and challenge the managing of many services. Consider what the implication on the design of the system will be, the risk of too many services, and whether the existing services can handle the new need.

Microservices boundaries are typically domain boundaries. So if you have two methods, both of them would conceptually access same back-end data structure, but each would serve a different business domain, then they fall under different microservices. For example, you might have some attendance tracking method and another method used to calculate payroll based on attendance. The first is used mainly for auditing purposes, to ensure we track who was in office when, while the other one is used to calculate working hours of an employee. Despite the fact that both of them would access same data (time in and time out) one would fall under audit microservice, while the other fall under payroll microservice.

To achieve the benefits of software reuse, teams may have to deal with sharing software through mono repo, libraries, or code redundancy in separate repositories. In this context, teams might accept this redundancy and deal with the need for increased coordination and dependency among them. One way to monitor this reuse is by adopting automation to identify and quantify the rate of code duplication growth.

Team expertise and familiarity with existing services Long-term maintenance costs Impact on system complexity Data consistency and transaction management Security and compliance requirements