Write latency, before and after eleven indexes

Eleven reporting indexes dropped from production tables, measured on the write path.

  orders INSERT p50     1.9ms → 1.1ms
  orders INSERT p99     8.4ms → 3.2ms
  order_lines INSERT    2.4ms → 1.2ms
  index storage         14.2 GB reclaimed
  buffer pool hit rate  99.1% → 99.6%

at 41,000 inserts a day the p50 saving is 33 seconds of
database time daily, which is nothing.

the p99 halving is not nothing. the buffer pool change
is the one that matters.

The median saving is trivial and the tail is not, which is the usual shape of an index-removal measurement. The buffer pool figure is the second-order effect and the reason this was worth doing — eleven indexes were occupying memory the working set now has.