Part 1: http://engineering.zenpayroll.com/how-ach-works-a-developer-perspective-part-1/ http://engineering.zenpayroll.com/how-ach-works-a-developer-... (HN: htt

Part 1: http://engineering.zenpayroll.com/how-ach-works-a-developer-perspective-part-1/ http://engineering.zenpayroll.com/how-ach-works-a-developer-... (HN: https://news.ycombinator.com/item?id=7636066 https://news.ycombinator.com/item?id=7636066) Part 2: http://engineering.zenpayroll.com/how-ach-works-a-developer-perspective-part-2/ http://engineering.zenpayroll.com/how-ach-works-a-developer-... (HN: https://news.ycombinator.com/item?id=7740967 https://news.ycombinator.com/item?id=7740967) Part 3: http://engineering.zenpayroll.com/how-ach-works-a-developer-perspective-part-3/ http://engineering.zenpayroll.com/how-ach-works-a-developer-... (HN: https://news.ycombinator.com/item?id=8007838 https://news.ycombinator.com/item?id=8007838)