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Erlang / Erlang Advanced Interview questions

What is a release in OTP and how does it differ from an application?

A release bundles a specific set of applications (your own plus the OTP applications they depend on, like kernel, stdlib, and sasl) together with a matching Erlang/OTP runtime version into one deployable, versioned unit — typically built with rebar3 release or similar tooling, producing a boot script and a self-contained directory tree you can ship to a server.

Where an application is one component (say, a payments service), a release is the complete, runnable system: every application it needs, pinned to specific versions, plus the runtime itself. This distinction matters most during upgrades — you can hot-swap an individual module inside a running application, but moving from one full release version to another (with dependency version changes, new applications, or config changes) is handled by release-level tooling (relup/release_handler), not simple module reloading.

What does an OTP release bundle together that a single application does not?
What handles moving a running system from one full release version to another?

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