Improve error messages in middleware

**Description**
Currently models lacks proper caching support.

**Proposed solution**
Add configurable caching with sensible defaults.

**Priority**: Low/Medium

The issue names middleware, models, and caching but provides no file, test, or entry point. First locate the middleware and model code, then identify existing caching behavior and tests; done should mean configurable caching with sensible defaults and covered error behavior.

Written by the indexing model from the issue text.