One revolution may obscure another. A new, more discreet trend is emerging from the Cloud, a trend which, however, may potentially drive in-depth changes in how we envisage IT operations : observability. This ebook presents observability, a new approach aimed at redesigning IT monitoring models and methods so as to adapt them to current paradigms, and provides insights into implementation as well as feedback and reports by various players in this field: Google Cloud, happn, Oui.sncf.