I think the primary difference is dependency.SOA and microservice aim to decouple application. The SOA emphasis "reuse",for example, there is a service named A that have some data including like name,age,etc.If other services want to use the data,either A expose a interface or A share their dataBase to others services.Regardless of which method you use,you must be sure A can provide service. If use microservice,i think the most thing is how making service which depends on A is more available to provide itself function.So it might use some redundant data in case A becomes unavailable.