You trouble is how model your microservices.
In term of microservices the second approach is most appropriate, which expose its logic through API.
Always when you model your microservices keep in mind the follow facts.
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Loose Coupling: When services are loosely coupled, a change to one service should not require a change to another. The whole point of this Microservice thing is being able to make a change to one service, and deploy it, independent of a need to change any other part of the system. This is really quite important.
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Strong Cohesion: We want related behaviour to sit together, and unrelated behaviour to sit elsewhere. Why? Well, if we want to change behaviour, we want to be able to change it in one place, and release that change as soon as possible.