Blockchain Architecture and Protocol Evolution: A Survey of Consensus, Forking, and Scalability Challenges

Blockchain systems rely on architectural design choices and consensus protocols to establish decentralized trust in distributed environments. This paper presents a focused survey of blockchain architecture and protocol evolution, emphasizing structural components, peer-to-peer networking, consensus mechanisms, forking models, and security-scalability trade-offs. Core elements such as blocks, cryptographic hashing, distributed ledgers, node roles, transaction propagation, and validation processes are examined to explain how integrity and immutability are maintained. Major consensus mechanisms, including Proof of Work (PoW), Proof of Stake (PoS), Practical Byzantine Fault Tolerance (PBFT), and Proof of Authority (PoA), are comparatively analyzed with respect to decentralization, throughput, finality, energy consumption, and deployment context. The paper also examines blockchain forking as a mechanism for protocol evolution and governance. By distinguishing protocol-level concerns from application-level adoption, this survey provides a technical foundation for evaluating blockchain systems and identifies open challenges in scalability, interoperability, governance, privacy, and sustainable consensus design.