The component of the SVM responsible for loading programs, enforcing account access rules (ownership, writability, signer checks), managing compute budgets, and executing transactions. The runtime ensures programs can only modify accounts they own, charges rent, and enforces the 10MB per-transaction account data limit.
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The component of the SVM responsible for loading programs, enforcing account access rules (ownership, writability, signer checks), managing compute budgets, and executing transactions. The runtime ensures programs can only modify accounts they own, charges rent, and enforces the 10MB per-transaction account data limit.
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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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Runtime (runtime) Category: Core Protocol Definition: The component of the SVM responsible for loading programs, enforcing account access rules (ownership, writability, signer checks), managing compute budgets, and executing transactions. The runtime ensures programs can only modify accounts they own, charges rent, and enforces the 10MB per-transaction account data limit. Related: Solana Virtual Machine (SVM), Sealevel, Transaction
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The Solana Virtual Machine—the execution environment that runs on-chain programs. SVM loads SBF bytecode, provides syscalls for account access and cryptographic operations, enforces compute budgets, and manages memory. The SVM is being modularized (via the SVM API) to enable use in rollups and other environments outside the main Solana validator.
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.
An atomic unit of execution containing one or more instructions, a recent blockhash, and one or more signatures. All instructions in a transaction execute sequentially and atomically—if any instruction fails, the entire transaction reverts. Transactions have a 1,232-byte size limit (matching IPv6 MTU) and a default 200,000 CU budget.
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A block that has reached maximum lockout depth in Tower BFT, meaning 31 or more consecutive confirmations have been built on top of it. Once a block becomes a root, it and all its ancestors are considered irreversibly finalized. The root corresponds to the 'finalized' commitment level in RPC queries and advances monotonically as the cluster processes new blocks.
A slot that has been finalized by achieving maximum lockout in Tower BFT—meaning 31+ consecutive confirmations have been built on top of it. Once rooted, a slot and its transactions are considered irreversible. Rooted corresponds to the 'finalized' commitment level and takes approximately 12-13 seconds.
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The Solana Virtual Machine—the execution environment that runs on-chain programs. SVM loads SBF bytecode, provides syscalls for account access and cryptographic operations, enforces compute budgets, and manages memory. The SVM is being modularized (via the SVM API) to enable use in rollups and other environments outside the main Solana validator.
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.
An atomic unit of execution containing one or more instructions, a recent blockhash, and one or more signatures. All instructions in a transaction execute sequentially and atomically—if any instruction fails, the entire transaction reverts. Transactions have a 1,232-byte size limit (matching IPv6 MTU) and a default 200,000 CU budget.
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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.