Orders Harmonization - Hardening Milestone

Overview

This is a placeholder issue to track and define activities around implementing tech debts, double/triple checking that features are working, stress testing/loading.

To be defined in collaboration with @jameslopez @tyleramos @vincywilson @ddavison @chloeliu

Test paths: https://docs.google.com/spreadsheets/d/1fjig4Sg37tJmKr4KODFfRDt91h6FYsSltTGBb7deKo4/edit#gid=0

cc: @jeromezng @adawar