Transaction throughput

For API request rate limits (GET/POST calls per second on Wallets endpoints), see Wallets API rate limits.

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Per-wallet queue limits

EVM blockchains use a mempool that queues pending transactions per sender address, up to a limit set by full nodes. Theoretical throughput is queueLimit / blockTime, though priority fees, congestion, and network liveness affect actual inclusion. Solana doesn’t use a mempool and has no per-account queue limit, which is one reason its throughput is significantly higher.

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Circle Wallets queue

To smooth over short bursts that exceed the blockchain limit, Circle Wallets queues additional transactions for a bounded duration. The service caps how many transactions a single wallet can hold in this queue. When you hit the cap, the API returns error code 155264:

Wait for pending transactions to be included on the blockchain before submitting new requests. EVM chains restrict the number of queued transactions per sender address.

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Monitor pending transactions

Use webhooks or the transactions API to track state changes on pending transactions.

• Webhooks (recommended): subscribe to webhook notifications for real-time state updates. More efficient than polling.
• Transactions API: call get transaction by ID, or list transactions filtered by state (INITIATED, CLEARED, QUEUED, SENT, or STUCK).

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Increase throughput

Three strategies scale throughput past the per-wallet ceiling:

• Raise the fee level: setting feeLevel: MEDIUM or HIGH prioritizes inclusion, which shortens confirmation time and reduces backpressure on subsequent transactions from the same wallet. See Gas fees for how fee levels work.
• Shard across multiple sender wallets: splitting sends across multiple wallets bypasses the per-wallet queue limit and increases parallelism. Works on every supported blockchain.
• Batch with smart contracts: for repetitive workloads, batch operations in a single contract call instead of sending individual transactions. For example, an airdrop contract that processes 500 transfers per call reduces 1,000,000 individual transfers to 2,000 batched calls. A batched call costs more gas per call than a single transfer, but the total gas and time saved make batching more efficient at scale. See the Airdrop template for Circle Contracts for a working example.

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Resolve stuck transactions

A STUCK transaction has been sent to the blockchain but can’t be included in a block because the network fee is below the current floor. This usually happens when gas prices spike during congestion, or when the feeLevel (or custom priorityFee/maxFee) is set too low. Resolve a stuck transaction two ways:

• Accelerate: call the accelerate transaction API to resubmit at the HIGH fee level.
• Cancel: call the cancel transaction API before the transaction is mined. Cancellation also incurs gas fees.

Monitor the new state using webhook notifications (recommended) or by polling the list transactions API.