Improve lookup time when adding billing account membership in cdot

Problem

Context: Adding a new billing account membership in customersdot admin: https://customers.gitlab.com/admin/billing_account_membership/new

When pasting a customer email in the Customer field, I have to wait for a lookup/search until a match is found and then I have to select the match from the list to be able to properly add the customer. This lookup time can be longer than 10 seconds.

It would be rare for an SE to manually type out the email, or to search for the customer by name. Since the full customer email is usually pasted in this field, can we make this lookup/search more performative?

The Billing account field is less slow, but has the same usage - we paste the full billing account number in the field, we do not type it out or search for a name.

Proposal

Improve the lookup time for the Customer and Billing account fields when adding a billing account membership in cdot admin.

Result

Being able to quickly populate the fields and add the new membership.

Next steps (if any)

How will we measure success?

Adding billing account membership takes less than 10 seconds.