A Survey on On-Chain-Off-Chain Scalability in Blockchain

Blockchain technology, providing security, trust, and transparency for a variety of applications, has become a revolutionary force in decentralized systems. However, scalability continues to be a major obstacle, restricting its use in large-scale and high-throughput settings. To assess the trade-offs between decentralization, security, and computing efficiency, our survey provides a thorough examination of both on-chain and off-chain scalability options, such as sharding, adaptive block sizing, rollups, state channels, and sidechains. Layered protocols (Layer 1 and Layer 2) are also discussed in terms of scalability and interoperability. By combining on-chain, off-chain, and modular blockchain designs, this work investigates new hybrid models, multi-layer architectures, and cross-chain scalability mechanisms in addition to conventional solutions. By identifying critical gaps and challenges in existing approaches, this survey provides a roadmap for future research in scalable, secure, and interoperable blockchain infrastructures, with applications in decentralized finance, IoT, and cross-border transactions.