Production throughput hinges on whether the active working set fits entirely within the WiredTiger cache. When the working set overflows available RAM, the engine repeatedly evicts and fetches pages from disk storage (cache thrashing), driving page faults upward and causing severe latency spikes on read paths.
Internal Architecture Breakdown
Production Inspection Queries
MongoDB
var s = db.serverStatus();
print('Page faults:', s.extra_info.page_faults, 'Bytes read into cache:', s.wiredTiger.cache['bytes read into cache']);