Task to be discussed at a follow-up interview.
- stress/load/performance tests; profiling; measurements
- custom JSON Unmarshal; parsing and facet sums calculations at once
- using search binary tree (map may speed up checks for each facet name being unique) for storing parsed facet names and their calculated sums => custom JSON Marshal
- unordered response => no need for sorting => custom response JSON Marshal
- concurrency
- unit tests for BadRequests