A period of 432,000 slots (approximately 2-3 days) that defines a staking cycle. At each epoch boundary, the leader schedule is recalculated based on stake weights, stake activations/deactivations take effect, and inflation rewards are distributed to validators and delegators.
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A period of 432,000 slots (approximately 2-3 days) that defines a staking cycle. At each epoch boundary, the leader schedule is recalculated based on stake weights, stake activations/deactivations take effect, and inflation rewards are distributed to validators and delegators.
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Think of it as part of the chain machinery that keeps ordering, execution, or consensus moving.
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Consensus, leader rotation, slots, epochs, and the runtime.
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Epoch (epoch) Category: Core Protocol Definition: A period of 432,000 slots (approximately 2-3 days) that defines a staking cycle. At each epoch boundary, the leader schedule is recalculated based on stake weights, stake activations/deactivations take effect, and inflation rewards are distributed to validators and delegators. Related: Slot, Leader Schedule, Stake-Weighted QoS (SWQoS)
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A time window during which a designated leader validator can produce a block. Each slot lasts approximately 400 milliseconds. Slots are numbered sequentially from genesis and grouped into epochs of 432,000 slots (~2-3 days). Not every slot produces a block—a skipped slot means the leader was offline or too slow.
A deterministic mapping of slots to validators for an entire epoch, computed from stake weights. Validators with more stake are assigned proportionally more leader slots. The schedule is derived using a seed from the previous epoch's randomness, so all validators independently compute the same schedule without coordination.
A Quality of Service system introduced in Solana that allocates TPU packet bandwidth to staked validators proportionally to their stake weight, preventing unstaked or lightly staked nodes from flooding leaders with transactions at the expense of stake-backed traffic. Validators that have delegated stake can forward transactions and receive preferential access to leader bandwidth, making it economically meaningful to route transactions through staked RPC or validator nodes. SWQoS is a key defense against spam and denial-of-service attacks that plagued Solana during high-traffic periods.
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A modular Layer-2 rollup launched on Ethereum mainnet in November 2024 that uses the Solana Virtual Machine (SVM) for execution, Celestia for data availability, and RISC Zero for zero-knowledge proofs. Eclipse brings SVM's parallel execution performance to Ethereum users with faster speeds and lower fees, hosting 60+ dApps across DeFi, gaming, and digital services.
An ordered unit within a block containing a mix of PoH ticks and transaction batches. Each entry includes a PoH hash, a count of hashes since the previous entry, and zero or more transactions. Entries without transactions are tick entries that advance the PoH clock; entries with transactions prove those transactions occurred between two points in time.
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A time window during which a designated leader validator can produce a block. Each slot lasts approximately 400 milliseconds. Slots are numbered sequentially from genesis and grouped into epochs of 432,000 slots (~2-3 days). Not every slot produces a block—a skipped slot means the leader was offline or too slow.
A deterministic mapping of slots to validators for an entire epoch, computed from stake weights. Validators with more stake are assigned proportionally more leader slots. The schedule is derived using a seed from the previous epoch's randomness, so all validators independently compute the same schedule without coordination.
A Quality of Service system introduced in Solana that allocates TPU packet bandwidth to staked validators proportionally to their stake weight, preventing unstaked or lightly staked nodes from flooding leaders with transactions at the expense of stake-backed traffic. Validators that have delegated stake can forward transactions and receive preferential access to leader bandwidth, making it economically meaningful to route transactions through staked RPC or validator nodes. SWQoS is a key defense against spam and denial-of-service attacks that plagued Solana during high-traffic periods.
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A clock mechanism that cryptographically proves the passage of time between events. PoH uses a sequential SHA-256 hash chain where each output becomes the next input, creating a verifiable ordering of events without requiring consensus. The leader produces ~400,000 hashes per slot (~400ms), and any validator can verify the sequence in parallel, enabling Solana's high throughput by removing the need for validators to agree on time.
Solana's custom BFT consensus algorithm built on top of Proof of History. Tower BFT uses PoH as a clock to reduce communication overhead in traditional PBFT from O(n²) to O(n). Validators vote on forks with exponentially increasing lockout periods—each consecutive vote doubles the lockout, making rollbacks progressively more expensive. A fork is finalized when it reaches supermajority (66.7%+ of stake).
A time window during which a designated leader validator can produce a block. Each slot lasts approximately 400 milliseconds. Slots are numbered sequentially from genesis and grouped into epochs of 432,000 slots (~2-3 days). Not every slot produces a block—a skipped slot means the leader was offline or too slow.
A set of entries produced by a leader during a single slot. A block contains transactions bundled into entries, each with a PoH hash proving ordering. Blocks are broken into shreds for network propagation via Turbine. Maximum block size is limited by compute units (48M CU cap per block) rather than byte size.