> For the complete documentation index, see [llms.txt](https://spire-docs.gitbook.io/spire/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://spire-docs.gitbook.io/spire/da-builder/architecture.md).

# Architecture

DA Builder's architecture consists of several key components that work together to aggregate and execute transactions efficiently. Below is an example showing how a rollup would setup an account with DA Builder and submit blob transactions to their inbox through DA Builder to save on costs:

### System Architecture

<figure><img src="/files/oddDm2O6raOnogcZxra8" alt=""><figcaption></figcaption></figure>

### Component Responsibilities

**User's EOA with EIP-7702 Proposer Code**:

* Contains the deployed proposer contract code (e.g., TrustlessProposer)
* Validates signatures and executes authorized transactions
* Signs transactions to be submitted to DA Builder

**DA Builder Service**:

* Accepts transaction submissions from users
* Validates EIP-7702 setup and account funding
* Collects multiple user transactions
* Creates aggregated EIP-4844 blob transactions
* Manages transaction ordering and batching
* Returns transaction IDs for tracking

**ProposerMulticall Contract**:

* Executes the aggregated transaction on-chain
* Calls each user's proposer contract in sequence

**GasTank Contract**:

* Stores user deposits to cover their respective transaction fees
* Provides balance tracking

**L2 Rollup Inbox**:

* Receives the actual user transaction
* Processes it according to L2 protocol rules
* Updates L2 state based on transaction execution


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