The exciting possibility to reshape the storage, transaction, logging, and recovery layers of next-generation systems on emerging hardware have prompted the database research community to vigorously debate the trade-offs between specialized kernels that narrowly focus on transaction processing performance vs. designs that permit transactionally consistent data accesses from decision support and analytical workloads. In this book, we aim to classify and distill the new body of work on transaction processing that has surfaced in the last decade to navigate researchers and practitioners through this intricate research subject.