> ## Documentation Index
> Fetch the complete documentation index at: https://protochain.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Transaction Service

> Compile, sign, simulate, and submit Solana transactions through the full lifecycle.

The Transaction Service manages the complete Solana transaction lifecycle — from draft construction through compilation, signing, and on-chain submission. Every transaction progresses through a defined set of states: DRAFT → COMPILED → PARTIALLY\_SIGNED → FULLY\_SIGNED → submitted. See the [Transaction Lifecycle](/concepts/transaction-lifecycle) concept page for a full walkthrough with state machine diagram.

## Methods

| Method                                                                                    | Description                                                                  | State Transition                             |
| ----------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------- | -------------------------------------------- |
| [CompileTransaction](/api-reference/transaction/compile-transaction)                      | Serialize a draft transaction to wire format, fetching the latest blockhash. | DRAFT → COMPILED                             |
| [EstimateTransaction](/api-reference/transaction/estimate-transaction)                    | Estimate compute units and fee lamports for a compiled transaction.          | None (read-only)                             |
| [SimulateTransaction](/api-reference/transaction/simulate-transaction)                    | Dry-run a transaction against current ledger state without committing it.    | None (read-only)                             |
| [SignTransaction](/api-reference/transaction/sign-transaction)                            | Add one or more cryptographic signatures to a compiled transaction.          | COMPILED → PARTIALLY\_SIGNED → FULLY\_SIGNED |
| [CheckIfTransactionIsExpired](/api-reference/transaction/check-if-transaction-is-expired) | Check whether a compiled transaction's blockhash has expired (\~150 slots).  | None (read-only)                             |
| [SubmitTransaction](/api-reference/transaction/submit-transaction)                        | Broadcast a fully signed transaction to the Solana network.                  | FULLY\_SIGNED → submitted                    |
| [GetTransaction](/api-reference/transaction/get-transaction)                              | Look up an on-chain transaction by signature.                                | None (read-only)                             |
| [MonitorTransaction](/api-reference/transaction/monitor-transaction)                      | Stream real-time status updates for a submitted transaction.                 | Streaming RPC                                |