> For the complete documentation index, see [llms.txt](https://docs.parallel.best/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.parallel.best/developers-hub/parallel-v2/classic-vaults/architecture.md).

# Architecture

<figure><img src="https://files.gitbook.com/v0/b/gitbook-legacy-files/o/assets%2F-MdnKrtV1Ev2ILZ6C4SC%2F-Mewj_rgbQXGsdrQ-2Bg%2F-MewoRAkAgeJuGYbz3MC%2FTitan_%20Architecture.png?alt=media&#x26;token=43ca7aef-588e-4424-a14d-ed23f7d1731a" alt=""><figcaption></figcaption></figure>

​The Parallel Protocol is a collection of decentralized and non-custodial smart contracts built to support the rest of the Decentralised Finance (DeFi) ecosystem:

* **Vaults Core:** The main contract to interact with the Parallel protocol. All calculations happen here.
* **Vaults Core State**: Owns the global state (cumulative rates & last refresh) for each collateral type available to borrow against. All state updates & calculations happen here
* **PAR**: PAR is a standard ERC20 tokens, whose value is pegged to the EUR fiat currency.
* **paUSD**: paUSD is a standard ERC20 tokens, whose value is pegged to the USD fiat currency
* **Rates Manager**: Stateless. Calculates debt and fees for each Vault.
* **Liquidation Manager**: Stateless. Calculates health factors and liquidation variables.
* **PriceFeed:** Responsible for retrieving collateral prices in fiat, for calculating Vault health factors.
* **FeeDistributor:** Responsible for collecting and distributing protocol fees.
* **AddressProvider:** Indexes all module addresses read by other modules.
* **ConfigProvider:** Responsible for updating protocol config parameters.
* **VaultsDataProvider:** Owns vault state, base debt, and vault related read functions.


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