How were updates performed in the shared database for individual microservices?

In a microservices architecture, sharing a single database among multiple services is usually avoided to prevent tight coupling. However, if a shared database is used, updates for each microservice are performed using transactions that ensure data integrity.

Common approaches include:

• Database-level transactions — each microservice performs its operations within a transaction to ensure atomicity.
• Optimistic locking — to prevent conflicts during concurrent updates.
• Event Sourcing and CQRS — updates occur through events that are applied to the database, allowing synchronization of state.

Example in Java using Spring and JPA:

@Transactional
public void updateEntity(EntityDto dto) {
    Entity entity = repository.findById(dto.getId())
        .orElseThrow(() -> new EntityNotFoundException());
    entity.setField(dto.getField());
    repository.save(entity);
}

Here, the @Transactional annotation guarantees that the update is performed atomically.