ntfy

Go single binary, no required external database (messages can be cached in-memory or a local key-value store), optional attachment storage on local disk.

Stateless-by-default design (topics are ephemeral pub-sub, not a persistent queue) means it scales horizontally behind a load balancer almost trivially; the only stateful concern is optional message caching, which can be disabled entirely for pure fire-and-forget scale.

A single pod with no dependencies is the entire deployment — set NTFY_BASE_URL to the Nexlayer domain. mirror.gcr.io/library/golang covers the build image; a small persistent volume is only needed if message caching/attachments are enabled.