pyth-evm

Fetch price update data from the Hermes API, then call updatePriceFeeds and read the price in a single transaction using getPriceNoOlderThan. Compute the fee dynamically with getUpdateFee and pass it as msg.value. Never expose updatePriceFeeds as a standalone public function, as this enables sandwich attacks.

Pyth uses a pull model where consumers fetch prices from the off-chain Hermes service and submit updates on-chain, while Chainlink pushes prices on-chain on a heartbeat schedule. Pyth offers sub-second latency and lower costs for high-frequency reads; Chainlink suits low-frequency monitoring without user transactions.

StalePrice means no recent price update exists on-chain. Pyth is a pull oracle, so you must call updatePriceFeeds with fresh Hermes data before reading. Also check that your maxAge parameter in getPriceNoOlderThan is not too strict and that cached Hermes data is not outdated.

Yes, feed IDs are bytes32 identifiers consistent across all EVM chains; for example, ETH/USD is always 0xff61491a931112ddf1bd8147cd1b641375f79f5825126d665480874634fd0ace. However, the Pyth contract address varies by chain, so verify the correct address for your target chain before deployment.

Pyth returns an int64 price with a negative int32 exponent, typically -8, so human-readable price equals price times 10^expo. The conf field is one standard deviation of uncertainty; reject prices where conf exceeds 1% of the price for lending protocols to avoid exploitation during volatility.

Express Relay is Pyth's MEV protection layer that routes liquidation opportunities through sealed-bid auctions instead of the public mempool, sending auction proceeds to your protocol. Use it for lending protocol liquidations on supported chains like Ethereum, Arbitrum, Base, and Optimism.