Microservices with shared database? using multiple ORM’s? [closed]

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You are not likely to benefit from a Microservices architecture if all the services share the same database tables. This is because you are effectively tightly coupling the services. If a database table changes all the services will have to change.

You have to understand that the whole reason for a Microservices architecture is to reduce dependencies between development teams and allow them to move ahead independently with fast releases.

Here is a quote from Werner Vogels, the Amazon CTO (Amazon pioneered a lot of the Microservices style architecture):

For us service orientation means encapsulating the data with the
business logic that operates on the data, with the only access through
a published service interface. No direct database access is allowed
from outside the service, and there’s no data sharing among the
services.

For more information read this and this.

An update in 2021:

Some commenters pointed out that sharing a physical DB may be ok, for example by using separate tables or schemas for different services in the same DB. This is of course possible and still a useful separation of concerns for the service development. It is an architectural (and also organizational-) decision if you want the service teams being responsible for the whole service stack and deployment, including infrastructure, or if you want to separate that out into an infrastructure- or devops-team. Each approach can have its pros and cons depending on your organizational circumstances, scale, requirements, etc.

Another aspect is that newer, scalable DB technologies are becoming more popular. They generally abstract storage and compute for separate scalability and are used as a service (for example Snowflake, Teradata, BigQuery, etc.). They allow growing to very large sizes with millions of tables and petabytes of content using a single cluster. With those it would be the goal to have the microservice implementation teams not worry about the details of running a DB infrastructure, but just use the DB cluster endpoint as a service dependency. And it would be the normal case to have many services depend on that same DB cluster. However you would still want to pay attention to storage separation, e.g. separate logical tables, collections, or whatever makes sense in the specific DB technology.

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