StreamChain: Do Blockchains Need Blocks?

Processing at block granularity and blockchains seem inseparable. The original role of blocks is to amortize the cost of cryptography (e.g., solving proof-of-work) and to make data transfers more efficient in a geo-distributed setting. While blocks are simple and powerful tool for amortizing these costs, today in permissioned distributed ledgers, that are often neither geo-distributed, nor require proof-of-work, the benefits of operating on blocks are overshadowed by the large latencies they introduce. Our proposal is to switch the distributed ledger processing paradigm from block processing to \emph{stream transaction processing} and rely on batching (i.e., block formation) only for amortizing the cost of disk accesses for commit operations. This paradigm shift enables shaving off end-to-end latencies by more than an order of magnitude and opens up new use-cases for permissioned ledgers. We demonstrate a proof-of-concept of our idea using Hyperledger Fabric, achieving end-to-end latencies of less than 10ms while maintaining relatively high throughput, namely close to 1500 tps.