DeFi Basics on Solana

8 examples to get you started with DeFi integrations - 5 basic and 3 intermediate. Covers swaps, AMMs, lending, LSTs, oracles, and composable CPI flows on Agave 4.1.1.

Prerequisites

• Solana CLI 3.0.10 on devnet for balance and token checks.
• @solana/kit 7.0.0 for TypeScript client examples.
• Familiarity with CPI Basics - most DeFi actions are CPI chains.

npm install @solana/kit@7.0.0 @solana/spl-token

Basic Examples

1. Read a Token Balance Before a Swap

Every DeFi action starts with knowing what the user holds.

import { createSolanaRpc, address } from "@solana/kit";
import { fetchMint, fetchToken } from "@solana-program/token";
 
const rpc = createSolanaRpc("https://api.mainnet-beta.solana.com");
const owner = address("YOUR_WALLET_PUBKEY");
const mint = address("EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v"); // USDC
 
const atas = await rpc.getTokenAccountsByOwner(owner, { mint }, { encoding: "jsonParsed" }).send();
console.log(atas.value);

• Balances live in SPL Token accounts, not the wallet pubkey directly.
• Always resolve the ATA (associated token account) for a mint before building swap instructions.
• Use jsonParsed to avoid manual layout decoding in clients.

Related: Swaps with Jupiter - routing after balance check

2. Quote a Swap via Jupiter API

Aggregators return a route and serialized transaction bytes.

const inputMint = "So11111111111111111111111111111111111111112"; // wSOL
const outputMint = "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v"; // USDC
const amount = "100000000"; // 0.1 SOL in lamports
 
const quoteRes = await fetch(
  `https://quote-api.jup.ag/v6/quote?inputMint=${inputMint}&outputMint=${outputMint}&amount=${amount}&slippageBps=50`
);
const quote = await quoteRes.json();
console.log(quote.outAmount, quote.routePlan);

• slippageBps is basis points (50 = 0.5%).
• The quote includes routePlan showing which AMM legs execute.
• Never hard-code pool addresses - routes change as liquidity shifts.

Related: AMMs (Raydium, Orca, Meteora) - what Jupiter routes through

3. Understand Constant-Product Pool Math

AMMs on Solana use the same x * y = k invariant as EVM DEXes, but state lives in program-owned accounts.

// Simplified constant-product output (fee omitted)
pub fn amount_out(amount_in: u64, reserve_in: u64, reserve_out: u64) -> u64 {
    let numerator = (amount_in as u128) * (reserve_out as u128);
    let denominator = (reserve_in as u128) + (amount_in as u128);
    (numerator / denominator) as u64
}

• Reserves are read from on-chain pool accounts at transaction build time.
• Stale reserves cause failed transactions or bad fills - refresh before send.
• Use checked math in programs; client previews can use u128 intermediates.

Related: AMMs (Raydium, Orca, Meteora) - pool layouts

4. Check an Oracle Price Feed

Lending and perps depend on fresh oracle prices.

import { createSolanaRpc, address } from "@solana/kit";
 
const rpc = createSolanaRpc("https://api.mainnet-beta.solana.com");
// Pyth SOL/USD price feed account (mainnet)
const priceAccount = address("H6ARHf6YXhGYeQfUzQNGk6rDNnLBQKrenN712K4AQJEG");
 
const account = await rpc.getAccountInfo(priceAccount, { encoding: "base64" }).send();
console.log(account.value?.data);

• Oracle accounts store price, confidence, and publish slot.
• Programs must check publish_slot staleness against a max age.
• Never trust client-side price reads for on-chain settlement.

Related: Oracles - Pyth and Switchboard integration

5. Wrap SOL to wSOL for AMM Swaps

Most pools quote against wrapped SOL, not native lamports in the wallet.

spl-token wrap 0.5
spl-token accounts

• spl-token wrap creates/funds the wSOL ATA and syncs native balance.
• Close the wSOL ATA after swaps to reclaim rent if you no longer need it.
• Jupiter routes often auto-handle wSOL, but manual CPI integrations must not.

Related: Swaps with Jupiter - wSOL in route legs

Intermediate Examples

6. Build and Send a Jupiter Swap Transaction

Turn a quote into a signed versioned transaction.

import { createSolanaRpc, createSolanaRpcSubscriptions, address } from "@solana/kit";
import { getBase58Codec } from "@solana/codecs-strings";
 
const swapRes = await fetch("https://quote-api.jup.ag/v6/swap", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    quoteResponse: quote,
    userPublicKey: "YOUR_WALLET_PUBKEY",
    wrapAndUnwrapSol: true,
    dynamicComputeUnitLimit: true,
  }),
});
const { swapTransaction } = await swapRes.json();
const txBytes = getBase58Codec().decode(swapTransaction);
// Sign and send with your wallet signer

• dynamicComputeUnitLimit simulates CU usage and sets a safe budget.
• wrapAndUnwrapSol handles wSOL lifecycle for SOL-involved routes.
• Simulate on devnet or Surfpool 0.12.0 before mainnet submission.

Related: DeFi Integrations Best Practices - slippage and simulation policy

7. Compose Lending CPI with Collateral Oracle

Money markets read oracle prices inside the borrow instruction.

// Anchor-style account validation sketch
#[account(
    constraint = oracle.key() == market.oracle_pubkey @ ErrorCode::BadOracle,
)]
pub oracle: AccountInfo<'info>,

• Lending programs CPI into oracle programs or read pre-loaded oracle accounts.
• Health factor checks must use the same price the liquidation engine uses.
• Test oracle staleness paths in LiteSVM 0.6.x before mainnet.

Related: Lending & Borrowing - Kamino and MarginFi patterns

8. Route Through an LST for Staking Yield

Liquid staking tokens trade like any SPL mint but represent staked SOL.

const jitoSolMint = "J1toso1uCk3RLmjorhTtrVwY9HJ7X8V9yYac6Y7kGCPn";
// Swap SOL -> jitoSOL via Jupiter, then deposit jitoSOL as collateral

• LSTs accrue yield via exchange rate, not rebasing balances.
• Integrations must use the correct mint (jitoSOL, mSOL, bSOL) per protocol allowlist.
• Sanctum routes unify LST liquidity across providers.

Related: Liquid Staking (LSTs) - mint addresses and rates

Stack versions: This page was written for Agave 4.1.1, Solana CLI 3.0.10, Anchor 0.32.1, anchor-lang 0.32.1, Rust 1.91.1, @solana/kit 7.0.0, Surfpool 0.12.0, and LiteSVM 0.6.x.