I don't think use of transactions or any other query or modeling hygiene are "internals". You can just as easily consider SQL to be an API (or really a DSL) for the black box of DB internals. In most cases, you're better off not looking inside the box because DB vendors only guarantee behavior at the API level. You can always identify and improve bottlenecks if/when they actually impact application function. I can write a load of crummy queries, expose them in an API and then just apply some clever caching and the DB will just never be a bottleneck no matter how little I understand it.