# Architecture overview

FastTrack is two pieces working together: a Chrome extension running in your browser, and a backend service that holds your custodial Solana wallet and signs transactions on your behalf.

## High-level flow

1. You install the extension. It overlays trading controls on every axiom.trade token page.
2. You generate a custodial wallet through the extension. The private key is encrypted and stored on our backend — never in the browser, never on disk.
3. You click a buy or sell preset.
4. The extension sends an authenticated request to our backend describing what you want to trade.
5. The backend builds a Solana transaction, signs it with your wallet, and submits it to the network.
6. On confirmation, cashback and referral rewards are credited to your account.

## Components

```
┌─────────────────────────┐         ┌──────────────────────────┐
│  FastTrack extension    │ ─────►  │  api.willet.cc           │
│  (Chrome / Brave / Edge)│  HTTPS  │  Rust backend (Axum)     │
└─────────────────────────┘         │                          │
                                    │  - Custodial signer      │
                                    │  - Routing engine        │
                                    │  - Ledger + rewards      │
                                    └──────┬───────────────────┘
                                           │
                                           ▼
                                    ┌──────────────────────────┐
                                    │  Solana RPC + landing    │
                                    │  services                │
                                    └──────────────────────────┘
```

## What the extension does

* Renders the trading overlay on axiom.trade.
* Detects which token page you are on.
* Sends authenticated requests to our backend.
* Displays your balance, tier, rewards, and claim history.
* **Never** holds your private key. **Never** signs transactions in-browser.

## What the backend does

* Holds the encrypted private key for your custodial wallet.
* Resolves which DEX a token trades on.
* Builds, signs, and submits trade transactions.
* Tracks your lifetime volume and tier.
* Accrues cashback and referral rewards on every confirmed trade.
* Pays out claims when you request them.

## What the backend does not do

* Make trading decisions on your behalf. You initiate every trade.
* Auto-sell, auto-stop-loss, or any form of automation.
* Hold your funds beyond the custodial wallet. Trading capital is in your wallet, on chain, at all times.

## Read more

* [Trade flow](/how-it-works/trade-flow.md) — what happens between click and confirmation.
* [Routing and execution](/how-it-works/routing.md) — how we pick the path for each trade.
* [Security model](/how-it-works/security-model.md) — threats, mitigations, and what's left to do.
* [Wallet custody](/how-it-works/custody.md) — the custodial model and how keys are protected.


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