DEFI Lending and Borrowing Explained: How It Works

What DEFI Lending and Borrowing Explained means

DeFi lending and borrowing is a blockchain-based arrangement in which software coordinates the supply of assets and access to credit-like liquidity. A supplier deposits assets into a protocol-defined mechanism; a borrower may obtain assets under rules encoded in or operated through the protocol. The specific assets, eligibility conditions, interest calculations, collateral requirements, and enforcement process depend on the implementation. “DeFi lending” therefore describes a family of designs, not one universal contract or operating model.

A useful way to define the system boundary is to separate three layers: settlement, application, and interface. The settlement layer records transactions and state changes on a blockchain. The application layer contains the protocol logic that determines what actions are accepted and how accounting is updated. The interface layer is the software through which a person or another application inspects and submits actions. These layers have distinct technical dependencies, but a particular system can distribute or combine them differently. [1]

This distinction matters when assessing claims about what a protocol does. A website may make an action easier to initiate, but it is not necessarily the protocol itself. Likewise, a contract’s documented behavior is not proof that a particular interface, network, asset, or deployment uses that contract correctly. The explanation below describes common architectural questions without assuming that every lending system shares the same mechanics.

Core components of DEFI Lending and Borrowing Explained

Participants and positions. Suppliers make assets available through the protocol’s supported mechanism. Borrowers request assets and, in many designs, maintain a position subject to protocol conditions. Other participants may operate interfaces, infrastructure, or services that expose protocol data or submit transactions. Their roles and permissions are implementation-specific; the term “decentralized” alone does not specify who can change parameters, pause functions, or upgrade software.

Contracts and application logic. On an EVM-compatible network, an application communicates with contracts using an interface description and encoded calls. Solidity’s contract ABI specifies the encoding of function selectors, arguments, return values, errors, and events. The application must use an ABI that matches the deployed contract interface and the network address it is calling. A mismatch can mean that the application is not describing the intended contract interaction, even if the transaction is otherwise well-formed. [2]

State and accounting. The protocol’s state is the recorded information used to determine balances and permitted actions. Depending on its design, relevant state may include supplied amounts, outstanding borrowing, collateral, accrued amounts, and parameters. These examples are questions to verify, not a claim that every protocol stores or calculates them in the same way. The contract code, deployment configuration, and current state together determine what a transaction can do at a particular moment.

External dependencies and interfaces. Users may rely on a wallet, an RPC endpoint, a block explorer, an interface, or data supplied to the protocol from outside its core contracts. Which dependencies matter depends on the design. A source pack for a particular deployment should establish whether it uses external data, how that data is delivered, and what happens when it is unavailable or stale. Do not infer those details from the broad label “lending protocol.”

How DEFI Lending and Borrowing Explained works

A generic interaction can be understood as a sequence of checks and state transitions. The exact sequence and available actions vary by protocol.

  1. Identify the deployment. The user or integrating application selects a network and contract address. The interface should be checked against the intended deployment, rather than assumed to represent every version of the protocol.
  2. Prepare a transaction. The application encodes a call using the contract’s ABI. The ABI must match the deployed contract interface and network address. The wallet presents the transaction for authorization; the chain processes it according to its transaction rules. [2]
  3. Supply assets, if the user is a supplier. The user submits the protocol-supported action to make assets available. The contract’s accepted conditions determine whether the transaction succeeds and how the resulting position is represented. The source pack does not establish universal deposit, withdrawal, or receipt-token mechanics, so these must be checked in the deployment’s documentation and code.
  4. Request assets, if the user is a borrower. The user invokes the protocol’s borrowing action, where available. The protocol evaluates the conditions implemented for that action and updates state if they pass. Whether collateral is required, how borrowing capacity is calculated, and what events can trigger enforcement are all implementation-dependent.
  5. Monitor and manage the position. Users and operators need a way to observe relevant state and understand which actions remain available. Events can help applications track contract activity, but event interpretation depends on the correct ABI and the deployed contract. A displayed value should be traced to its source and calculation rather than treated as an independent guarantee.
  6. Repay, withdraw, or resolve the position. The protocol may expose actions for repayment and for withdrawing supplied assets, subject to its rules and current state. The order, partial-action support, fees, and conditions cannot be generalized from the term “DeFi lending.” Verify the relevant contract functions and operational documentation for the selected version.

This flow is a map for investigation, not a universal transaction recipe. A protocol may bundle steps, use multiple contracts, or rely on additional services. Its documentation should connect user-facing actions to contract functions, state changes, and any prerequisites.

Trust and control boundaries

A transaction accepted by a contract demonstrates that the contract processed the call under its current rules; it does not by itself establish that the rules are appropriate, that the interface displayed them accurately, or that a user can reverse the action. The contract, the application that constructs calls, the wallet that authorizes them, and the network that records them are separate parts of the operational path.

Control questions include who can change parameters, replace or upgrade contracts, pause actions, or manage supported assets. The answers must be established for the specific deployment. The available accepted claims do not identify common admin arrangements or establish that any particular lending protocol is immutable, decentralized in a particular governance sense, or recoverable after an incident.

Liquidity also needs careful framing. The PFMI liquidity-risk principle says designated financial market infrastructures must manage sufficient liquid resources in relevant currencies to meet settlement obligations under normal and stressed conditions. That principle can serve as an operational analogy when asking how crypto payment or settlement infrastructure handles obligations, but PFMI applies to designated FMIs; it does not make every crypto product an FMI or establish that a lending protocol meets the standard. [3] For a specific protocol, examine its own liquidity mechanisms and evidence rather than importing a formal standard by analogy.

Limitations and failure modes

Implementation mismatch. An interface can encode a call using an ABI that does not match the deployed contract or can point to an unintended network address. The ABI specification makes the interface dependency explicit; verification must connect the ABI, address, and network. [2]

State or service visibility gaps. A user-facing display is mediated by software and data sources. If an interface, RPC service, or indexer is unavailable or presents incomplete information, the user may have difficulty assessing a position even if the underlying contract remains deployed. Which services a protocol depends on, and what fallback paths exist, require deployment-specific evidence.

Liquidity and execution constraints. The ability to initiate an action is not the same as assurance that every participant can complete every desired action under all conditions. Operational analysis should identify obligations, available resources, and behavior during stress. The PFMI principle is a useful question prompt, not proof of a crypto protocol’s liquidity or a directly applicable rule for all products. [3]

Rules are not uniform. Collateral, rates, fees, liquidation or other enforcement mechanics, supported assets, and governance controls cannot be inferred from the category name. Any claim about these features needs evidence for the particular protocol, version, network, and review date. A general description should not imply predictable returns, guaranteed access to funds, or recovery after a failure.

What teams should verify

Before integrating with or operating a lending protocol, teams can build an evidence record around the following questions:

  • Deployment identity: What network and contract addresses are in scope? Do the deployment records and official documentation identify the same version?
  • Interface correctness: Does the ABI match the deployed contract interface and address? Can each application action be mapped to a function, arguments, expected return behavior, emitted events, and possible errors? [2]
  • Transaction path: Which wallet, RPC, interface, and other services construct, authorize, relay, or display the interaction? What is the documented fallback if one is unavailable?
  • State and position rules: Which contract state determines supply, borrowing, repayment, and withdrawal eligibility? Which calculations or external inputs affect those actions? Confirm each answer from version-specific documentation or code rather than assuming a standard design.
  • Control and change process: Who can alter parameters, pause functions, or change the deployment? What evidence documents those permissions and the process for changes?
  • Operational liquidity: What obligations may arise, what resources are intended to meet them, and how does the system describe stressed conditions? Treat formal standards as applicable only where their scope actually fits; use analogies only as prompts for analysis. [3]
  • Evidence freshness: When were the documentation, code, and deployment details reviewed? Record version and date, because interface and protocol behavior may change.

The central lesson is that DeFi lending and borrowing is best understood as a specific deployment’s combination of settlement, application logic, interfaces, state, and operational dependencies. The label gives a starting point; contract-level and service-level verification establishes what a particular system actually permits and relies on.

Sources and references