What is Solana?

Proof of History: how the clock works

Proof of History (PoH) is not a consensus mechanism by itself — it is a timekeeping mechanism that works alongside Solana's consensus layer. It uses a Verifiable Delay Function (VDF): a computation that takes a predictable, irreducible amount of time to run, but whose output can be quickly verified by others.

A PoH generator continuously runs SHA-256 in a loop, hashing its own previous output. Each hash output — with its count — serves as a cryptographic timestamp. Because SHA-256 is sequential (each hash requires the previous one), and because the count is verifiable, the sequence proves that a specific amount of time elapsed between any two events in the chain. Transactions are inserted into this hash sequence, timestamping them cryptographically without requiring any external agreement.

This means validators do not need to communicate with each other to agree on transaction order — the PoH sequence already establishes it. They can validate transactions in parallel, dramatically increasing throughput.

Solana's architecture: eight innovations

The Solana whitepaper describes eight technical innovations that together enable its performance. The most significant beyond PoH are: Tower BFT (a PoH-optimised version of PBFT consensus that leverages the PoH clock to reduce messaging overhead), Turbine (a block propagation protocol that breaks data into small packets and uses a tree structure for efficient dissemination across validators), Gulf Stream (a mempool-less transaction forwarding protocol that pushes transactions to validators before the current block is finalised), and Sealevel (a parallel smart contract runtime that executes non-overlapping transactions simultaneously on all available cores).

Sealevel is particularly important for DeFi: because Solana contracts declare which accounts they will read or write in advance, the runtime can determine which transactions are independent and execute them in parallel — something Ethereum's EVM cannot do natively.

SOL tokenomics

SOL has no hard cap — new SOL is continuously issued as staking rewards. The initial inflation rate at mainnet launch was 8% annually, with a planned 15% reduction each year until reaching a long-term target of 1.5% annually. As of 2026, inflation is approximately 4–5% annually. A portion of transaction fees is burned, partially offsetting issuance.

Validators and delegators who stake SOL earn rewards from this inflation. The Solana staking system uses a delegated proof-of-stake model: SOL holders can delegate their stake to validators without giving up custody of their tokens, earning a proportional share of validator rewards.

The Firedancer client — technical significance

Prior to Firedancer, Solana had one validator client — the Agave client (originally called Solana Labs client). A single client implementation is a significant risk: a bug in that one codebase can take down the entire network, as happened during Solana's 2022 outages. Firedancer is a fully independent rewrite in C by Jump Crypto, providing client diversity for the first time. With two independent clients, a bug in one does not halt the network — the other continues operating. This is the same reason Ethereum has multiple client implementations (Geth, Nethermind, Besu, Erigon).