When does a spelling become correct?

Here are three links that are worth your time.

• When does a spelling become correct? – When did the word Expresso become Espresso? Wolfram blog details on the journey of the missing X in Espresso.
• Scaling time-series data storage – Netflix’s post on scaling time-series data storage is a great engineering read. Particularly because they operate at the scale of tens of millions of users. It discusses the use of Cassandra (a NoSQL database management system) and challenges in tweaking it for better practices.
• Pandas stack and unstack operations