Who said anything about microservice architecture?
If you're building a new MVP that needs background processing, you have a queue, and your monolith listens to the queue. Sticking to one database during the MVP keeps things simple until you validate both the product and expected scale. You can migrate to something heavier later if the product gets traction.
If you're building a new MVP that needs background processing, you have a queue, and your monolith listens to the queue. Sticking to one database during the MVP keeps things simple until you validate both the product and expected scale. You can migrate to something heavier later if the product gets traction.