Technical Reference

Blockchain in Payments

Working principles, network types, consensus mechanisms, DeFi protocols, stablecoins, and CBDCs — a technical guide to blockchain technology and its integration with modern payment infrastructure.

3–5 sXRPL / Stellar finality

$300B+stablecoin supply (DefiLlama, 2026)

130+countries exploring CBDCs (Atlantic Council)

21MBTC supply cap

Solana Architecture

Solana uses an account model where every piece of state (including token balances) lives in a separate account. Transactions reference accounts as read-only or writable. Proof of History (PoH) timestamps each transaction, enabling ~65 000 TPS (theoretical) with ~400ms slots.

Concept	Solana	Ethereum analogue
Native currency	SOL (lamports, 1 SOL = 10⁹)	ETH (wei, 1 ETH = 10¹⁸)
Token standard	SPL Token	ERC-20
Smart contracts	Programs (Rust/SBF)	Contracts (EVM bytecode)
Account state	Separate accounts	In-contract storage
Consensus	PoH + Tower BFT	PoS Gasper
Block time	~400ms	~12s
Finality	~1 s optimistic · ~13 s finalized (32 slots)	~12.8 min (2 epochs)
Typical fee	$0.00001–$0.001	Cents to dollars (varies with gas price)

SPL Token Payment flow

1. Token mint & ATAs

Each SPL token has a Mint account. Users hold balances in Associated Token Accounts (ATAs) — separate accounts owned by the Token Program.

2. Transfer instruction

Sender calls spl-token Transfer, referencing source ATA, destination ATA, and authority (sender keypair). No separate approve needed for P2P.

3. Block confirms

Transaction lands in the next ~400 ms slot. Optimistic confirmation follows in about a second; the ‘finalized’ commitment after 32 slots (~13 seconds).

4. Settlement

Recipient’s ATA balance updates. No reversals possible; no chargeback risk.

Solana Pay Specification

Solana Pay defines two request types encoded in a QR-scannable URI scheme, making it suitable for point-of-sale integration.

Transfer Request

Simple SOL or SPL-token transfer. The wallet constructs and signs the transaction automatically.

SOL transfer

solana:mvines9iiHiQTysrwkJjGf2gb9Ex9jXJX8ns3qwf2kN
 ?amount=1.5
 &label=Acme+Coffee
 &message=Order+%23A42
 &memo=ORDER-A42

USDC transfer (SPL token)

solana:mvines9iiHiQTysrwkJjGf2gb9Ex9jXJX8ns3qwf2kN
 ?spl-token=EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v
 &amount=10.00
 &label=Acme+Coffee

Transaction Request

For complex payments (loyalty, NFT receipts, conditional logic), the merchant provides an API endpoint. The wallet POSTs its account address; the endpoint returns a partially signed transaction for the wallet to complete.

URI points to a merchant backend (a link with a query string must be URL-encoded)

solana:https%3A%2F%2Fapi.merchant.com%2Fpay%3ForderId%3DA42

1. Wallet scans QR

Reads Solana Pay URI pointing to merchant’s API endpoint.

2. Wallet GETs metadata

Fetches label and icon from endpoint (GET request).

3. Wallet POSTs account

Sends its public key to the endpoint. Merchant uses it to build a custom transaction.

4. Merchant returns tx

API responds with a serialized, partially signed transaction (base64 encoded).

5. Wallet signs & submits

User confirms; wallet adds their signature and broadcasts to the Solana network.

URI parameters

Parameter	Type	Description
`amount`	decimal	Transfer amount (SOL or token units)
`spl-token`	address	SPL token mint address; omit for SOL
`label`	string (URL-encoded)	Merchant name shown in wallet
`message`	string	Human-readable description
`memo`	string	On-chain memo instruction (SPL Memo)
`reference`	address (repeatable)	Public keys for payment tracking