Which is actually very relevant to the project that I’m referring to. All four services were database intensive. They all worked perfectly independently. But when messages started at service 1, did some database work and put a message in the queue to kick off the next process and so on. When all four were running at the same time processing messages, the database screamed and made the website unresponsive.

It took me longer to tune performance than to write the code. Can you imagine four developers working together tweaking code, queries, indexes, number of simultaneous threads, etc?