# High-level System Architecture

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### Numpay System Architecture

Numpay’s protocol is designed for fast, low-cost, and secure global transactions using familiar identifiers like phone numbers and email addresses. The architecture is composed of core modules that work together to abstract blockchain complexity while preserving transparency and control.

<figure><img src="/files/uB1dpJutIlz1XXmU75vD" alt=""><figcaption></figcaption></figure>

#### 1. User Input

The transaction starts with a simple input: an email or phone number. This is all the sender needs to identify the recipient. There’s no need for wallet addresses, bank details, or app downloads.

#### 2. Identity Abstraction Layer (IAL)

The input is passed to the Identity Abstraction Layer, which maps the identifier to a blockchain wallet. This mapping is handled securely using encrypted attestations and public key infrastructure. The system verifies that the identifier is linked to an active wallet before proceeding.

* Identity proofs are signed by a verifier network.
* Mapping is stored off-chain and validated on-chain before transaction execution.

#### 3. Transaction Routing Engine

Once the destination is resolved, the Transaction Routing Engine selects the most efficient execution path on Solana. It evaluates network load, transaction priority levels, and validator performance in real time to optimize for cost, speed, and confirmation reliability.

* Dynamically adjusts **compute units and priority fees** for faster confirmations when the network is busy.
* Supports **batched and parallelized instructions** to reduce transaction overhead.
* Includes **fallback routing** through alternate RPC endpoints or relayer nodes to maintain uptime during congestion.

#### 4. Smart Contracts

All transfers are executed via smart contracts. These contracts manage resolution, token transfers, optional settlement logic, and gasless transaction handling.

* Contracts are modular and upgradeable
* All logic is verifiable on-chain

#### 5. **Relayer for Gasless Execution**

To remove the need for users to pay network fees, Numpay uses a **fee-payer relayer system** on Solana. Relayers act as sponsors by covering the transaction fees and are later reimbursed through the protocol’s reward pool or staking incentives.

* Uses Solana’s **fee-payer feature**, allowing the relayer’s wallet to sign and pay for the transaction on behalf of the user.
* Transactions include **user signatures for authorization**, ensuring full security and replay protection.
* Relayers can be **decentralized nodes** selected through staking and verified activity, maintaining fairness and reliability.

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