Observational Transient Astrophysics in the era of « big data », DESI and the ULTRASAT satellite

We have entered a golden age for studying astrophysical “transients”. Recent advances in the field of large-scale, high-cadence astronomical surveys have provided unprecedentedly rich and diverse data sets and transient astronomy is said to have entered a “big data era”. I will give a short overview of several on-going and future instruments which are real « game-changers » in the field and will show how combining their assets, as well as using tools from « data science » - involving high-performance computing and data mining - can lead to promising new science. I will then share recent results from the first UV survey of the early evolution of interacting supernovae and from mining twenty years of X-ray archival data in search for the shortest transients, including the elusive signatures of the mysterious supernova «shock breakout».