# A Review on Decentralized Finance Ecosystems
## 4 The Taxonomy
### Product/Services
#### 4.2.1 Payments  
The Bitcoin blockchain is widely acknowledged as an early and prominent instance of a DeFi application. Although initially designed as a P2P payment system without smart contract functionality, it has garnered extensive adoption as a decentralized payment system. The emergence of solutions leveraging the Ethereum network and smart contracts has facilitated decentralized payment services and spurred diverse app innovations [31]. Smart contracts, digital programs stored on a blockchain network, automate transaction execution based on predetermined conditions. They enable the execution of agreements and transactions among anonymous parties, eliminating the need for intermediaries or central institutions. Smart contracts also enable the automation of predetermined events, such as interest or dividend payments, without manual intervention [8].  
Payments in the DeFi ecosystem use P2P systems and smart contracts to facilitate transactions, promoting financial inclusion, streamlining payment processes, and maximizing security, efficiency, transparency, and cost-effectiveness. Smart contracts ensure secure, efficient, and cost-effective domestic and cross-border transactions, including those involving cryptocurrencies, while eliminating the need for intermediaries and reducing the risks associated with fraud and transaction delays. Smart contracts also eliminate the possibility of missed opportunities in trade finance and commodity trading [88; 91]. DeFi offers diverse payment solutions, with _Sablier_ standing out as a real-time finance protocol. It enables continuous payments over time rather than in a single transaction, finding applications in payroll processing, micro-consulting, and time-sensitive engagements. _Sablier_ operates through a smart contract, allowing gradual fund allocation set by the payment stream creator. Recipients can withdraw funds at any time, making it akin to an everyday payday. Payments in any ERC-20 token are supported, providing senders the flexibility to cancel streams if needed, with the remaining funds returned to them upon cancellation. Another DeFi payment application akin to _Sablier_ is _Connext_. It operates as a layer 2 payment channel network, enabling instant, cost-effective payments without requiring on-chain transactions. This efficiency makes it suitable for various use cases, such as streaming payments and micropayments. Leveraging blockchain programmability, _Connext_ offers a scalable and user-friendly payment solution within the DeFi ecosystem. _Ripple_ operates as a blockchain-based digital payment network, facilitating the transfer of digital and fiat currencies internationally without intermediaries in real time. Its blockchain, XRPL, tracks transaction details like accounts and balances. Primarily focused on payment settlement, asset exchange, and remittance, _Ripple_ resembles SWIFT in facilitating international money and security transfers for banks and financial institutions. Its consensus mechanism aims to prevent double-spending, enhancing system integrity. Despite not being a DeFi platform, _Ripple_'s innovative features hold the potential to revolutionize the financial industry, particularly in cross-border payments and remittances.