Let's add transactions to FPGA-based key-value stores!

In recent years we have seen a proliferation of FPGA-based key value stores (KVSs) 1--3, 5--7, 10 driven by the need for more efficient large-scale data management and storage solutions. In this context, FPGAs are useful because they offer network-bound performance even with small key-value pairs and near-data processing in a fraction of the energy budget of regular servers. Even though the first FPGA-based key-value stores started appearing already in 2013 and have evolved significantly in the meantime, almost no attention has been paid to offering transactions. Today, however, that such systems are becoming increasingly practical, we need to ensure consistency guarantees for concurrent clients (transactions). This position paper makes the case that adding transaction support is not particularly expensive, compared to other parts of these systems, and in the future all FPGA-based KVSs should provide some form of transactional guarantees. In the remaining of this paper we present a high level view of the typical pipelined architecture of FPGA-based KVSs that most existing designs follow, and show three different ways of implementing transactions, with increasing sophistication: from operation batching, through two phase locking (2PL), to a simplified snapshot isolation model