Our team at Bitloops has just published a Todo app that we think you'll find very interesting as a reference implementation. It's designed to showcase some advanced software architecture concepts like Hexagonal Architecture, DDD, BDD, CQRS, and Event Driven Architecture.
We've used a variety of open source technologies, such as TypeScript, NestJS, gRPC, Jaeger, Prometheus, NATS JetSteam, Grafana, Mongo, Postgres, and more to build a clean and modular codebase that's as close to production-ready as possible.
We know that learning these concepts and technologies can be challenging, which is why we wanted to share with you this comprehensive example we wish we had available when we started learning these concepts.
Check it out https://github.com/bitloops/ddd-hexagonal-cqrs-es-eda and we would love to hear your feedback. Let us know what you think and if you like it please star!