I Built a REST Microservice With a Database in 3 Files — and Wrote Zero Code

Description and use

A REST microservice backed by SQLite, fully defined in three HCL configuration files with no application code. Mycel automatically provides the HTTP server, routing, validation, transformation, retries, and health/metrics/debug endpoints.

Problem

Developers spend excessive time writing boilerplate plumbing for microservices, leading to repetitive code for routing, validation, database access, and error handling.

Outcome

A production‑ready REST microservice running in two minutes, with CRUD endpoints, validation, data transformation, retries, and built‑in health/metrics/debug, all defined in three configuration files and requiring no application code.

Workflow

• 1. Create SQLite database schema via CLI
• 2. Write three HCL files: config.mycel, connectors/connectors.mycel, flows/flows.mycel
• 3. Define service name and version in config.mycel
• 4. Declare connectors for REST API and SQLite database
• 5. Define flows mapping API operations to database targets
• 6. (Optional) Add validation, transformation, and error handling blocks inside flows
• 7. Build or pull Mycel Docker image
• 8. Run Mycel container mounting config directory and exposing port

Evidence

Mycel scans the config directory recursively, so the file layout is yours to choose — one file or fifty.

Source

Now hit the API like any other REST service: ... A working CRUD microservice. Zero lines of Go, JavaScript, or anything else.

Source