Deploying a Multi-Module Spring Boot App to Render with PostgreSQL, Redis, Docker, and Flyway

Deploying a Spring Boot backend should be simple in theory. Build the JAR, set the environment variables, connect the database, and ship it.

In practice, my deployment exposed several assumptions that worked locally but failed immediately in the cloud.

I recently deployed a modular Spring Boot application to Render using Docker, Render Blueprint, PostgreSQL, Redis, Flyway migrations, Spring profiles, Hibernate/JPA, and environment variables.

The application worked locally with MySQL and Redis, but deployment exposed several production-specific issues that were easy to miss in local development. This article documents the problems, why they happened, and how I fixed them properly.

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