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.
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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.
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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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Slot (slot) Category: Core Protocol Definition: 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. Related: Block, Epoch, Leader Schedule
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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.
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.
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.
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Solana's parallel transaction execution engine. Sealevel can process thousands of transactions simultaneously by analyzing each transaction's declared account inputs—transactions that don't touch the same writable accounts run in parallel across available CPU cores. This account-level parallelism is what enables Solana's high throughput.
The smallest unit of block data propagated through the network via Turbine. Blocks are split into shreds of up to 1,228 bytes each (fitting in a single UDP packet). Shreds are Reed-Solomon erasure coded—typically 32 data shreds produce 32 recovery shreds—so blocks can be reconstructed even if up to half the shreds are lost.
A serialized copy of the full accounts state at a rooted slot, used for fast validator bootstrapping. Full snapshots contain all accounts; incremental snapshots contain only accounts modified since the last full snapshot. New validators download a snapshot instead of replaying the entire ledger history, reducing sync time from days to minutes.
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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.
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.
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.
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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 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.
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.