For Elixir I saw a simple distributed job scheduler - it was dead simple in code and was ripped, because it didn’t require maintenance for ~8 years just working without issue and people who knew anything about it left company or switched part of company and acted as they forgot everything.
The other example is medium sized (in terms of features and code) web app - maintained by <30 people now, delivering more than 800 people at the other company, no stress, no issues and with great DX because of the BEAM (other company is drowning in JVM based nano-services).