# Concurrent Transactions ## Overview Tempo's concurrent nonce system lets a single account send multiple transactions in parallel, without waiting for each one to confirm sequentially. By using different nonce keys, transactions that don't conflict can execute simultaneously, significantly improving throughput for high-activity accounts. [See the Tempo Transactions specification](https://docs.tempo.xyz/protocol/transactions/spec-tempo-transaction) ## Recipes These recipes assume you have [set up a Tempo client](/tempo). ### Send in Parallel Submit multiple transactions at once with `Promise.all`. Viem assigns non-conflicting nonce keys automatically. :::code-group ```ts twoslash [example.ts] import { client } from './viem.config' const [receipt1, receipt2] = await Promise.all([ client.sendTransactionSync({ data: '0xcafebabe00000000000000000000000000000001', to: '0xdeadbeefdeadbeefdeadbeefdeadbeefdeadbeef', }), client.sendTransactionSync({ data: '0xdeadbeef00000000000000000000000000000002', to: '0xfeedfacefeedfacefeedfacefeedfacefeedface', }), ]) ``` ```ts twoslash [viem.config.ts] filename="viem.config.ts" // [!include ~/snippets/tempo/viem.config.ts:setup] ``` ::: ### Control Nonce Keys For finer control, assign each transaction a distinct `nonceKey` so they cannot conflict. Nonce keys must be greater than `0` (key `0` is reserved for protocol nonces). :::code-group ```ts twoslash [example.ts] import { client } from './viem.config' const hash1 = await client.sendTransaction({ data: '0xcafebabe00000000000000000000000000000001', nonceKey: 567n, // [!code focus] to: '0xdeadbeefdeadbeefdeadbeefdeadbeefdeadbeef', }) const hash2 = await client.sendTransaction({ data: '0xdeadbeef00000000000000000000000000000002', nonceKey: 789n, // [!code focus] to: '0xfeedfacefeedfacefeedfacefeedfacefeedface', }) ``` ```ts twoslash [viem.config.ts] filename="viem.config.ts" // [!include ~/snippets/tempo/viem.config.ts:setup] ``` ::: ### Read a Nonce Read the current nonce for an account and nonce key with [`nonce.getNonce`](/tempo/actions/nonce.getNonce). :::code-group ```ts twoslash [example.ts] import { client } from './viem.config' const nonce = await client.nonce.getNonce({ account: '0xcafebabecafebabecafebabecafebabecafebabe', nonceKey: 567n, }) ``` ```ts twoslash [viem.config.ts] filename="viem.config.ts" // [!include ~/snippets/tempo/viem.config.ts:setup] ``` ::: ## Best Practices ### Use Distinct Nonce Keys per Stream Give each independent stream of transactions its own `nonceKey`. Transactions that share a nonce key are still ordered relative to each other, so reuse a key only when ordering matters and use separate keys to maximize parallelism. ## See More