Here is a 1-paragraph summary of the text: This post demonstrates how to use a database as a persistence layer for a JavaScript microservices application. The authors show how to use Netflix Eureka and Netflix Zuul for service discovery and load balancing, and how to add a cloud-based MongoDB Atlas database as a persistence layer. They provide a hands-on introduction to working with MongoDB Atlas and demonstrate how to scale the services by adding new instances to the system. The post also covers how to update services while maintaining 100% system uptime, using a persistence layer that stores data in a shared database.