My stab at the things we should measure without values to measure them against:
- Response time for find as you type search search (average, 99th percentile, and 99.9th percentile)
- Response time for full text search (average, 99th percentile, and 99.9th percentile)
- User perceived accuracy of full text search
Now - these are based around how the system currently sits and somewhat ignorant of how mobile works - meaning they are almost certainly wrong. So fix them. Please.