This is a great article for anyone interested in measuring a system's performance. Simme Aronsson shows how to measure Service Levels Indicators, Objectives and Agreements and how to plan for Error Budgets.
It may sound like a simple question to answer but Gregory Paciga correctly noticed there's more to that. It's hard to disagree!
Yannis Ragkavas reflects on his approach to testing (or lack of) when he was a software developer and shares a few accurate pieces of advice on how it can be improved.
Speaking of developers, Gaurav Singh put a lot of effort into explaining Who the heck is an SDET?.