Mainframe-era applications are typically monolithic and massive. They are centralized, inflexible, closed, and expensive to maintain. Then, we came across client-server and multi-tier distributed applications. There are business-domain-specific applications that solve specific problems. There are web, cloud, social, enterprise, mobile, wearable, and IoT applications. Then, there are operational, transactional, and analytical applications. With the solidity of microservices, all kinds of software applications get disintegrated into a number of microservices, which are very famous for facilitating easy integration, deployment, management, and manoeuvrability. Microservices are self-defined and hence autonomous.

They can be developed and deployed independently. Microservices are being stuffed with their own data stores. Microservices are decoupled, so dependency issues don't crop up. However, to create and sustain bigger and better applications, different and geographically-distributed microservices need to be found and fused systematically. That is, services should be matched and composed to realize composite applications, which are right and relevant for enterprise and cloud IT. Not only for enterprise applications but also for creating integrated and insightful applications, the act of composition acquires special significance.

Composition is being accomplished in two prominent ways—orchestration and choreography. As mentioned in the The emergence of cloud-native applications section, there are domain-specific and neutral applications that innately need the blending of multiple microservices to fulfil varying business requirements, market sentiments, and user expectations. In short, the composition of microservices deserves the highest recognition for producing smarter applications towards user-empowerment. Hence, to realize all kinds of smart applications, API-stuffed, extensible, configurable, interoperable, and composable microservices are the need of the hour. Composition tools and techniques are flourishing, and hence service composites are the best fit for constructing insight-driven, highly sophisticated, and integrated applications that can run on any runtime (bare-metal servers, virtual machines, containers, and functions). In addition, the future calls for device-centric cloud environments, which are aptly termed fog or device clouds. Microservice composites can run not only on resource-intensive servers but also on resource-constrained and networked devices, which is the real beauty of microservices.