  In 2020, while main database conferences one by one had to adopt a virtual
format as a result of the ongoing COVID-19 pandemic, we decided to hold VLDB
2021 in hybrid format. This paper describes how we defined the hybrid format
for VLDB 2021 going through the key design decisions. In addition, we list the
lessons learned from running such a conference. Our goal is to share this
knowledge with fellow conference organizers who target a hybrid conference
format as well, which is on its way to becoming the norm rather than the
exception. For readers who are more interested in the highlights rather than
details, a short version of this report appears in SIGMOD Record.
