Skip to content
Web3 Academy

Lending pool

Reading depth

Each view includes the earlier layers; the complete engineer or auditor page is shown by default.

A lending pool aggregates supplied assets, issues supplier claims, and makes available liquidity borrowable under interest and risk rules.

Split balance category cue

A lending pool aggregates supplier assets, issues supplier claims, and lets borrowers draw available liquidity under interest and risk rules.

Why it exists

Section titled “Why it exists”

A bilateral lender must find, underwrite, fund, monitor, and settle one borrower. A pool standardizes those rules and reuses capital across many participants. That coordination creates a shared balance sheet: one borrower’s default or one accounting error can affect other suppliers.

Traditional-finance analogy

Section titled “Traditional-finance analogy”

A pooled credit fund or bank lending book is a useful analogy. A smart contract can automate balances, rates, collateral checks, and liquidation, but oracles, governance, liquidators, token issuers, administrators, and backstops remain. A supplier claim is not automatically a protected or instantly redeemable deposit.

Both sides of the position

Section titled “Both sides of the position”

The same supplied asset can appear as pool cash or a borrower receivable, but not as two unrelated net assets. Supplier tokens are debt claims and conditional redeemable claims, represented as claim tokens, whose value depends on cash, debt repayment, interest, reserves, and losses.

Lifecycle and state changes

Section titled “Lifecycle and state changes”
  1. A supplier transfers assets and receives or accrues a pool claim.
  2. A borrower pledges eligible collateral.
  3. The pool transfers available cash and records borrower debt.
  4. Interest increases debt and allocates value among suppliers, reserves, and fees.
  5. Repayment restores cash and reduces debt.
  6. Withdrawal burns or reduces a supplier claim and transfers available assets.
  7. Unsafe positions enter liquidation; unrecovered value becomes bad debt.

Capital flow is supply, borrow, repay, liquidation repayment, and withdrawal. Claim flow is the supplier position and borrower debt. Return flow starts with borrower interest and any explicit incentives. Risk flow reaches reserves, backstops, or suppliers when collateral recovery and borrower repayment are insufficient.

Return source and liquidity boundary

Section titled “Return source and liquidity boundary”

Borrowers pay interest. Protocol token incentives are a separate issuance source. The supplier rate can be lower than the borrower rate because not every supplied unit is borrowed and reserves or fees take part of the accrual. Accrued claim value is not the same as immediately withdrawable cash: high utilization can make a solvent pool temporarily illiquid.

Engineer or auditor lens

Section titled “Engineer or auditor lens”

Reconcile cash, total supply claims, total debt, interest indices, reserves, fees, collateral, and realized loss. Test first and final supplier, zero cash, high utilization, accrual gaps, rounding, caps, unusual tokens, repayment on behalf, withdrawal ordering, liquidation, write-off, pauses, upgrades, and backstop use. Illiquidity and insolvency must not be silently conflated.

Aave’s V3 introduction describes one pooled, overcollateralized model and its supplier claims. Compound III documentation describes a base-asset lending market with separate collateral balances. These references, reviewed 2026-08-09, illustrate different implementations rather than one universal pool accounting model.

Common misunderstandings

Section titled “Common misunderstandings”
  • “Supplied means available to withdraw.” Borrowed assets can leave little current cash.
  • “Overcollateralized means no lender loss.” Prices, liquidity, oracles, execution, and code can defeat recovery.
  • “Interest is generated by the pool.” Borrowers pay interest; incentives and reserve income are separate sources.

Continue with utilization and rates.

Machine-readable model

Key equations

Canonical expressions come from the structured concept record. KaTeX renders the notation, while the plain-text expression and variable table keep its meaning and units inspectable without JavaScript. Read the narrative above for the model's domain, assumptions, and rounding rules.

This concept does not require one canonical equation. Its mechanism and state transitions remain the authoritative explanation; do not invent a formula merely to make the topic look quantitative.

Interactive module

Test the mechanism

Change collateral, debt, risk limits, and elapsed time; inspect health, borrowing capacity, shocks, and liquidation.

Open Lending and liquidation lab on its full lab page

Assurance contract

Security properties

These structured statements define desired behavior. Their stable IDs can bind tests, invariants, specifications, audit findings, or proof results without turning descriptive review advice into an assurance claim.

Desired · not evaluated: No test, audit, or proof result is implied until scoped evidence is linked to this property.

  1. SP-01Desired · not evaluated

    Supplier claims and borrower debts reconcile with accountable pool assets, cash, interest, reserves, and realized losses

  2. SP-02Desired · not evaluated

    Borrowing cannot exceed the selected collateral and capacity rules

  3. SP-03Desired · not evaluated

    Repayment cannot reduce debt below zero and withdrawal cannot transfer more liquid assets than the claim permits

  4. SP-04Desired · not evaluated

    Insolvency, illiquidity, reserve use, and loss socialization remain explicit in accounting

Knowledge check

Quiz

Answer in your own words, then open the model answer.

What problem does Lending pool exist to address?

Model answer

Lending pools coordinate many suppliers and borrowers so capital can be reused without requiring each lender to underwrite and settle one bilateral loan.