This paper introduces Bitcoin-NG, a scalable blockchain protocol designed to address the scalability limitations of Bitcoin and other Bitcoin-derived protocols. Bitcoin-NG maintains the same trust model as Bitcoin but decouples blockchain operation into two planes: leader election and transaction serialization. This separation allows for better latency and bandwidth performance while maintaining Byzantine fault tolerance and robustness to extreme churn. The protocol introduces key blocks for leader election and microblocks for transaction serialization, with each epoch having a single leader responsible for serializing state machine transitions. The security of Bitcoin-NG is based on incentive compatibility, ensuring that participants are motivated to follow the protocol rules. The paper also introduces several novel metrics to evaluate the security and efficiency of Bitcoin-like blockchain protocols, including consensus delay, fairness, mining power utilization, subjective time to prune, and time to win. These metrics help in quantifying the performance and security of the protocols. Large-scale experiments on a 1000-node emulation testbed, representing 15% of the operational Bitcoin network, demonstrate that Bitcoin-NG scales optimally. The bandwidth is limited only by the processing capacity of individual nodes, and latency is limited only by network propagation time. Bitcoin-NG outperforms Bitcoin in terms of consensus delay and bandwidth, while maintaining or improving security-related metrics such as fairness and mining power utilization. The experiments show that Bitcoin's frequent forks lead to higher latency, reduced fairness, and increased mining power concentration, which are not issues in Bitcoin-NG due to its design. The paper concludes with a discussion of related work, highlighting the differences between Bitcoin-NG and classical Byzantine fault-tolerant replicated state machines (RSMs) and other scalable blockchain protocols like GHOST.This paper introduces Bitcoin-NG, a scalable blockchain protocol designed to address the scalability limitations of Bitcoin and other Bitcoin-derived protocols. Bitcoin-NG maintains the same trust model as Bitcoin but decouples blockchain operation into two planes: leader election and transaction serialization. This separation allows for better latency and bandwidth performance while maintaining Byzantine fault tolerance and robustness to extreme churn. The protocol introduces key blocks for leader election and microblocks for transaction serialization, with each epoch having a single leader responsible for serializing state machine transitions. The security of Bitcoin-NG is based on incentive compatibility, ensuring that participants are motivated to follow the protocol rules. The paper also introduces several novel metrics to evaluate the security and efficiency of Bitcoin-like blockchain protocols, including consensus delay, fairness, mining power utilization, subjective time to prune, and time to win. These metrics help in quantifying the performance and security of the protocols. Large-scale experiments on a 1000-node emulation testbed, representing 15% of the operational Bitcoin network, demonstrate that Bitcoin-NG scales optimally. The bandwidth is limited only by the processing capacity of individual nodes, and latency is limited only by network propagation time. Bitcoin-NG outperforms Bitcoin in terms of consensus delay and bandwidth, while maintaining or improving security-related metrics such as fairness and mining power utilization. The experiments show that Bitcoin's frequent forks lead to higher latency, reduced fairness, and increased mining power concentration, which are not issues in Bitcoin-NG due to its design. The paper concludes with a discussion of related work, highlighting the differences between Bitcoin-NG and classical Byzantine fault-tolerant replicated state machines (RSMs) and other scalable blockchain protocols like GHOST.