> For the complete documentation index, see [llms.txt](https://docs.zetrix.com/zetrix-l2-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.zetrix.com/zetrix-l2-documentation/architecture/overall-architecture.md).

# Overall Architecture

## High-Level Architecture

At the highest level, Z2 is a pipeline: users submit transactions through wallets and RPC endpoints; a **Sequencer** orders them into batches and posts a commitment to the L1 inbox while the data goes to the **Data Availability Committee (DAC)**; a **Main Proposer Validator** proposes an assertion of the resulting state; the **Committee** (Validators + Reexecutors, 5 members, 3-of-5) verifies and signs that assertion for **soft confirmation** and manages the DAC; and **Watchers** (the Proposer's own watcher role plus external operators) fetch data from the DAC, re-execute, and may raise disputes on L1. Supporting services provide observability, operations, bridging, and developer access.

![L2 High Level Architecture](/files/3Zg9ObXz5oyrVP3fBQD4)

The diagram above shows the full deployment and how the parts interact:

* **Ecosystem Support** — Refueler, Monitoring, Explorer, Zetrix MCP, and Faucet.
* **Z2 Node cluster** (go-quorum QBFT) feeds a set of **Sequencers** that **batch data and send it to the L1 inbox** on the **Zetrix Node (L1)**.
* **Z2 Relayer** relays messages **from L1 to L2** (e.g. deposits).
* **Layer 2 Committee** (Validator/Aggregator + Reexecutor, with its **DA/DAC** store) **verifies and signs the proposed assertion for soft confirmation** and manages the temporary L2 data availability.
* **Main Validator** (Proposer + Watcher) **proposes new assertions** to L1.
* **External Validators** (Watcher + Reexecutor) **fetch L2 data from the DAC** and re-execute to detect any mismatch, disputing when needed.

Components group by the **plane** each part lives in:

| Plane                      | Contains                                                                            | Role                                                              |
| -------------------------- | ----------------------------------------------------------------------------------- | ----------------------------------------------------------------- |
| **L2 Execution**           | Z2 Nodes (go-quorum QBFT), Sequencer, Reexecutor (independent Besu replay)          | Order transactions, produce blocks, cross-client re-execution     |
| **Data Availability**      | Validator Committee, Aggregator, DAC                                                | Attest/serve batch data (AnyTrust); verify & sign the assertion   |
| **Zetrix L1 (settlement)** | Sequencer Inbox, Rollup, Bridge & Outbox                                            | Record batches, hold assertions, custody bridged assets, finalize |
| **Services**               | Proposer, Watchers, Relayer, Refueler, Explorer, Monitoring, MCP, Faucet, z2-signer | Propose/verify assertions, bridge, operate, observe, sign (HSM)   |

> **Validator roles.** *Proposer* — proposes a new assertion. *Watcher* — verifies the soft-confirmed assertion and disputes on mismatch. The Main Validator runs both roles; External Validators run the Watcher role and can **earn a reward** for an honest dispute.

> **Layer 2 Committee.** The Committee verifies and signs the assertion created by the Proposer, and manages the temporary L2 **data availability (DAC)** mapped to the commitment posted by the Sequencer. **Each committee bundle runs on a separate server — 5 committees, requiring 3-of-5 for voting.**

## Data Flow Summary

| Stage | Component                          | Responsibility                                                           | Output                  |
| ----- | ---------------------------------- | ------------------------------------------------------------------------ | ----------------------- |
| 1     | Wallet                             | Sign transactions                                                        | Signed tx               |
| 2     | RPC / LB                           | Accept, route, rate-limit                                                | Forwarded tx            |
| 3     | Z2 Nodes                           | Mempool, EVM execution, QBFT block production                            | Blocks                  |
| 4     | Sequencer                          | Order transactions; post commitment to L1 inbox; publish data to DAC     | Commitment + data       |
| 5     | Main Proposer                      | Propose assertion of resulting L2 state                                  | Proposed assertion      |
| 6     | Committee (Validator + Reexecutor) | Fetch data, re-execute, verify & sign the assertion (3-of-5); manage DAC | Soft confirmation       |
| 7     | Watchers                           | Fetch data from DAC, re-execute, dispute on mismatch                     | Fraud proof (if needed) |
| 8     | Zetrix L1                          | Settlement, dispute resolution, finality                                 | Final confirmation      |

## Trust and Confirmation Timeline

```mermaid
sequenceDiagram
    participant User
    participant Seq as Sequencer
    participant DAC as DAC
    participant Prop as Main Proposer
    participant Comm as Committee
    participant L1 as Zetrix L1
    participant Watch as Watchers

    User->>Seq: Submit transaction
    Seq->>Seq: Order into batch
    Seq->>L1: Post batch commitment (L1 inbox)
    Seq->>DAC: Publish tx data
    Prop->>L1: Propose assertion (state claim)
    Comm->>DAC: Fetch data & re-execute
    Comm->>L1: Verify & sign assertion (3-of-5)
    Comm-->>User: Soft confirmation (fast)
    Note over L1,Watch: Challenge window opens
    Watch->>DAC: Fetch data & re-execute
    Watch->>L1: Dispute if mismatch
    L1-->>User: Final confirmation (after window)
```

***

[← Introduction](/zetrix-l2-documentation/introduction.md) · [Index](/zetrix-l2-documentation/readme.md) · [Trust Model →](/zetrix-l2-documentation/architecture/trust-model.md)