Crypto glossary
Compute units (Solana fees)
Compute units measure how much processing a Solana transaction uses; they cap its workload and set the price of the optional priority fee.
Every Solana instruction consumes compute units as it runs, similar to gas on Ethereum. A transaction has a compute budget: by default up to 200,000 units per instruction and a maximum of 1.4 million per transaction. Developers can request a specific limit, and blocks also have an overall cap on the units they can contain.
Solana fees have two parts. A base fee of 5,000 lamports per signature is charged regardless of complexity. On top of that, users can add a priority fee, priced in micro-lamports per compute unit and multiplied by the requested limit. When the network is busy, wallets and bots raise that price to get their transactions processed first, especially when they compete for the same accounts.
Requesting too many compute units wastes money on the priority fee, while requesting too few makes the transaction fail. Because Solana schedules transactions by the accounts they write to, congestion can be local: a hot memecoin pool may be expensive to touch while the rest of the chain stays cheap. Bots spamming transactions have still caused periods of severe congestion.
Example
A trading bot sets a compute limit of 150,000 units and a price of 10,000 micro-lamports per unit, adding a priority fee of 1.5 billion micro-lamports, or 0.0015 SOL, plus the base fee.