Microservice architectural style is an approach to developing a single application as a suite of small services.

Services are built around business capabilities , independently deployable and packaged, each running in its own process.

Each Service should have separate database layer.

Each Service can have independent codebase, CI/CD tooling sets.

Each Service can be tested in isolation without dependent on other services.

Each service can pick the best technology stack for its use cases (no need to stick into one framework throughout the entire application).

Each Service should have monitoring and troubleshooting capabilities for operation team

Services should implement Retry functionality in case of network failure or system failure

Each Service can implement independent security mechanism

The main difference between SOA and MicroServices is that a microservice employs a practice that attempts to eliminate any dependencies on other microservices. SOA does not make this

practice explicit as a requirement.

Services can use HTTP(Rest) or messaging for communication or any other lightweight communication protocol.

Well understood Distribution Transaction management

Presenting API

Clean and Clear Separation of Stateless and Stateful Services

Do Not Share Libraries or SDKs

Each Service can be run without waiting for other service to go online

Implement a Self-Registration and Discovery Mechanism

Service can use different language,framework and technologies

Maintain Independent Revisions and Build Environments to maintains compatibility with other services.

An architect can explicitly check for rules and constraints. 

https://medium.com/@anilkkurmi/20-characteristics-of-microservices-architecture-fbd3da151384