The key differences between SOA and microservices are as follows:

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SOA Microservices

Follows “share-as-much-as-possible” architecture approach   Follows “share-as-little-as-possible” architecture approach

Importance is on business functionality reuse   Importance is on the concept of “bounded context”

They have common governance and standards   They focus on people collaboration and freedom of other options

Uses Enterprise Service bus (ESB) for communication Simple messaging system

They support multiple message protocols They use lightweight protocols such as HTTP/REST etc.

Multi-threaded with more overheads to handle I/O    Single-threaded usually with the use of Event Loop features for non-locking I/O handling

Maximizes application service reusability   Focuses on decoupling

Traditional Relational Databases are more often used    Modern Relational Databases are more often used

A systematic change requires modifying the monolith A systematic change is to create a new service

DevOps / Continuous Delivery is becoming popular, but not yet mainstream    Strong focus on DevOps / Continuous Delivery