SumUp
Software EngineerFoundationalAug 6, 2026

Eliminate duplicate chip-payment receipt events

Small checkout defects often become trust problems before they become large incidents.

Fast recovery behavior can conflict with the need for a single, unambiguous record of a sale.

When it prints twice, people look at me like I charged them twice.

Nisha Patel · Bakery owner

Runs a small counter-service bakery and uses a terminal with a receipt printer for each sale.

What pulls against what

  • fast retry behavior vs. single-sale clarity
  • patch speed vs. regression coverage
  • merchant reassurance vs. peripheral timing

What is at stake

A small device retry defect is making completed sales look uncertain. A precise fix restores confidence at the counter

Why SumUp

At SumUp, these moments often matter because merchants rely on checkout signals to keep a queue moving.

Written for

Reliability-minded product engineerEmbedded systems debuggerPayments platform engineer

This is the setup. The work is inside.

Running it puts you in the room: the full situation and its constraints, stakeholders who push back in their own words, and the decisions that are yours to make. What you produce becomes a Day One Plan — work you can show someone instead of describing.