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

# Architecture

### High-level Architecture

<figure><img src="/files/FX9SykAqOjhpyh7GMOs8" alt=""><figcaption><p>High-level Architecture</p></figcaption></figure>

In Futaba, [Relayer](/docs/protocol/relayer.md) and [Konoha (Oracle)](/docs/protocol/konoha.md) are the off-chain components and they receive the Src (Source) chain requests. Relayer then retrieves the storage proof from each chain, and [Konoha](https://app.gitbook.com/o/Thz2mfuoktjdE6MeG8yW/s/sOs4pzHyvFKixViaeh5C/~/changes/26/protocol/konoha) retrieves the block headers and returns them to the Src chain for validation.

### Detailed Architecture

<figure><img src="/files/WXOhQcZYa1VHfJPuYbrk" alt=""><figcaption><p>Detailed architecture</p></figcaption></figure>

**Phase 1: request query**

1. Call the endpoint to request a [Gateway Contract](/docs/protocol/gateway.md) query from the user contract
2. [Gateway Contract](/docs/protocol/gateway.md) emits events related to query requests to [Relayer](/docs/protocol/relayer.md)
3. An event about the query of the block header is emitted from [Light Client Contract](/docs/protocol/light-client.md) to [Konoha (Oracle)](https://app.gitbook.com/o/Thz2mfuoktjdE6MeG8yW/s/sOs4pzHyvFKixViaeh5C/~/changes/26/protocol/konoha)

**Phase 2: off-chain agents work**

* [Konoha](/docs/protocol/konoha.md)
  1. [Konoha](/docs/protocol/konoha.md) receives the event and gets the block header (state root) for a specific block height in the destination chain
  2. Return and save state root to [Light Client Contract](/docs/protocol/light-client.md)
* [Relayer](/docs/protocol/relayer.md) work
  1. [Relayer](/docs/protocol/relayer.md) receives the event and obtains the account proof and storage proof of the target data
  2. Return the proof to the [Gateway Contract](/docs/protocol/gateway.md) in the src chain (at this time, the state root must have been saved first)

**Phase 3: verify and return data to the user**

1. [Light Client Contract](/docs/protocol/light-client.md) to verify account proof and storage proof
2. The store received data as a cache
3. If verification is successful, data is returned to User Contract