> Name one Rust realworld app older than 5 years that is in this category.
Your "older than 5 years" requirement isn't really fair, is it? Rust itself had its first stable release barely 10 years ago, and mainstream adoption has only started happening in the last 5 years. You'll have trouble finding any "real-world" Rust apps older than 5 years!
As to your actual question: The users of Ferrocene[0] would be a good start. It's Rust but certified for ISO 26262 (ASIL D), IEC 61508 (SIL 4) and IEC 62304 - clearly someone is interested in writing mission-critical software in Rust!