Performance

The engine keeps request-time work small. There is no published benchmark suite for it yet; measure your own templates before relying on specific numbers.

What the design does

1. Parse at startup. {{…}} delimiters are found once in Setup::run(); no parsing or regular expressions at request time.
2. Compiled templates. Each template is compiled once into a binding plan; a render resolves each distinct placeholder name once, sizes one String and writes static text and values into it.
3. Borrowed values. Params returns Cow<str>, so struct fields and HashMap values are copied straight into the output.
4. Shared read lock. Lookups take a read lock on an RwLock<HashMap>; many requests can read at once. Engine::get returns an Arc<Template>, so a lookup never copies the template.
5. Signing cost. Keys are decoded and validated once in Setup::run(). HMAC-SHA256 and Ed25519 signing run once per envelope over the v2 message, which allocates the message bytes. Unsigned engines build no message.