An entry in a block that contains one or more transactions along with a PoH hash proving their temporal ordering. Unlike tick entries (which contain zero transactions and only advance the clock), transactions entries represent actual state changes. Transactions within a single entry are eligible for parallel execution if they do not share writable accounts.
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An entry in a block that contains one or more transactions along with a PoH hash proving their temporal ordering. Unlike tick entries (which contain zero transactions and only advance the clock), transactions entries represent actual state changes. Transactions within a single entry are eligible for parallel execution if they do not share writable accounts.
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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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Transactions Entry (transactions-entry) Category: Core Protocol Definition: An entry in a block that contains one or more transactions along with a PoH hash proving their temporal ordering. Unlike tick entries (which contain zero transactions and only advance the clock), transactions entries represent actual state changes. Transactions within a single entry are eligible for parallel execution if they do not share writable accounts. Related: Entry, Tick, Block, Parallel Transaction Execution
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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.
A PoH entry with zero transactions that advances the clock. There are 64 ticks per slot by default, each representing a fixed number of SHA-256 hash iterations. Ticks establish the passage of time even when no transactions are being processed, maintaining the PoH chain continuity.
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.
Solana's ability to process multiple transactions simultaneously by analyzing their account access lists and executing non-conflicting transactions in parallel across CPU cores via the Sealevel runtime. Two transactions can run in parallel only if they do not share any writable accounts; transactions sharing a writable account are serialized. This design allows Solana to fully exploit modern multi-core hardware and is a primary contributor to its high throughput.
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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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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.
A PoH entry with zero transactions that advances the clock. There are 64 ticks per slot by default, each representing a fixed number of SHA-256 hash iterations. Ticks establish the passage of time even when no transactions are being processed, maintaining the PoH chain continuity.
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.
Solana's ability to process multiple transactions simultaneously by analyzing their account access lists and executing non-conflicting transactions in parallel across CPU cores via the Sealevel runtime. Two transactions can run in parallel only if they do not share any writable accounts; transactions sharing a writable account are serialized. This design allows Solana to fully exploit modern multi-core hardware and is a primary contributor to its high throughput.
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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.