There are not many improvement opportunities left to support the growing demand of BrownField Airline's business. BrownField Airline was looking to re-platform the system with an evolutionary approach rather than a revolutionary model.

Microservices is an ideal choice in these situations—for transforming a legacy monolithic application with minimal disruption to the business:

As shown in the preceding diagram, the objective is to move to a microservices-based architecture aligned to the business capabilities. Each microservice will hold the data store, the business logic, and the presentation layer.

The approach taken by BrownField Airline is to build a number of web portal applications targeting specific user communities such as customer facing, front office, and back office. The advantage of this approach lies in the flexibility for modeling, and also in the possibility to treat different communities differently. For example, the policies, architecture, and testing approaches for the Internet facing layer are different from the intranet-facing web application. Internet-facing applications may take advantage of CDNs (Content Delivery Networks) to move pages as close to the customer as possible, whereas intranet applications could serve pages directly from the data center.