VLDB 2021: Designing a Hybrid Conference

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.