Scalability issues in blockchain technology is a significant research area that focuses on overcoming limitations in transaction throughput, latency, and network capacity in decentralized systems. Traditional blockchains, such as Bitcoin and Ethereum, face inherent bottlenecks due to consensus mechanisms, block size limits, and sequential transaction validation, which hinder mass adoption and high-frequency applications. Research explores layer-2 solutions (e.g., Lightning Network, Plasma), sharding, sidechains, off-chain processing, DAG-based architectures, and consensus optimization techniques to enhance throughput and reduce latency. Recent studies also investigate hybrid blockchain models, parallel processing, adaptive block generation, and cross-chain scalability frameworks. Applications span cryptocurrencies, decentralized finance (DeFi), supply chain management, IoT networks, healthcare, and large-scale decentralized applications (dApps). Current research emphasizes the trade-offs between scalability, security, and decentralization (the blockchain trilemma), as well as energy efficiency, network resilience, and interoperability, establishing scalable blockchain architectures as essential for enabling practical, high-performance decentralized systems.