Blockchain for large-scale applications explores how decentralized ledger technology can be adapted and optimized to meet the high performance, scalability, and reliability demands of real-world enterprise and societal use cases. Research in this area investigates challenges such as transaction throughput, latency, interoperability, storage efficiency, and energy consumption when blockchain is deployed across massive networks with millions of users or devices. Studies emphasize applications in sectors like global finance, supply chain management, healthcare, Internet of Things (IoT), e-governance, and smart cities, where large-scale adoption requires robust architectures and consensus mechanisms that balance decentralization with efficiency. Techniques such as sharding, sidechains, layer-2 protocols, and hybrid blockchain models are proposed to overcome bottlenecks while ensuring transparency, fault tolerance, and security. By addressing these issues, research provides frameworks and optimized protocols that enable blockchain to scale seamlessly and operate effectively in complex, data-intensive environments