Tan, Hao2025-07-032025-07-032025-07-032025-05-05https://hdl.handle.net/10012/21964Blockchains are decentralized ledger technologies that provide secure, transparent, and tamper-resistant transaction records. Permissioned blockchains restrict participation to authorized entities and employ Byzantine Fault Tolerance (BFT) protocols for consensus. As blockchain systems evolve, the need for exchanging data and assets across heterogeneous networks has grown. To support such functionality, platforms increasingly integrate with external systems, enabling information flow between decentralized and conventional infrastructures. Blockchain oracles serve a key role in this integration by injecting real-world data—such as asset prices or event outcomes—into smart contracts through structured oracle data feeds. Conventional blockchain systems typically employ BFT consensus for oracle data integration, which introduces substantial latency and computational overhead. Although consensus protocols offer robust consistency guarantees, they also incur significant computational and communication overhead, thereby constraining system responsiveness and scalability in blockchain environments. To address these challenges, this thesis investigates weaker coordination protocols as lightweight alternatives that relax strict consistency requirements while preserving sufficient reliability for practical deployment. This thesis evaluates the effectiveness of these protocols in enhancing the performance of read-write operations—a common access pattern in oracle data feed processing—across three distinct projects. First, this thesis assesses the overhead of consensus in key-value processing by comparing consensus protocols with shared register protocols. The comparison reveals two previously overlooked limitations that arise under workload-driven access patterns. Second, it introduces a shared register protocol tailored for wide-area networks, which employs loosely synchronized clocks and asymmetric quorum techniques to reduce coordination latency across heterogeneous client loads. Third, it applies weaker coordination techniques to oracle data feed processing—a fundamental component of many smart contract applications. By decoupling data feed processing from BFT consensus using a probabilistic quorum protocol and a censorship-resistant broadcast primitive, the proposed design improves both throughput and data freshness for on-chain transactions dependent on timely off-chain inputs. Collectively, these contributions demonstrate how workload-specific weaker protocols can enable more efficient distributed systems. By reducing coordination overhead without sacrificing practical correctness, the proposed approaches support the development of scalable, responsive, and application-aware decentralized infrastructures.endistributed systemsByzantine fault tolerancestate machine replicationblockchainDoctoral Thesis