Shared internals of Stratum's starters: the switch that turns each module on or off, how a module's settings combine properties and Java configuration, and the error and warning codes with the error objects every module reports.

Test support: the helpers and checks that several Stratum modules' tests share, and PostgreSQL and Redis containers for services' integration tests.

Metrics, traces and health, sent over OTLP to an OpenTelemetry Collector, with safe defaults.

Structured JSON logs in one format, with the service's name and environment on every line and secrets and personal data redacted before anything is written.

What stratum-starter-webmvc and stratum-starter-webflux share: the web settings and the error format.

The rules that mask secrets and personal data in text, shared by stratum-starter-logging and stratum-starter-observability.

What the HTTP client starters share: the @StratumClient annotation, the settings of each client and the module's codes.

Spring's caching switched on, with bounded Caffeine caches by default and safe Redis defaults on Spring Boot's own keys.

Spring Security's OAuth2 client, without its web lock-down, for the service token of an HTTP client's auth.client-credentials.