What is DeFi? Banking without the bank, with the risk
Lending, borrowing, and trading run by smart contracts. Liquidations, liquidity pools, yield farming, why bridge hacks cost hundreds of millions, and a checklist before trying it.
DeFi means decentralized finance: lending, borrowing, and trading run by smart contracts on a blockchain instead of by a bank. No account manager, no opening hours, no permission. You connect a wallet, and the code either does the deal or it does not. Tens of billions of dollars sit in these contracts today, and both the genuinely new ideas and the fastest thefts in finance live here.
The pitch is real. The risks are just as real, and they arrive without a complaints department.
How does DeFi lending work?
Overcollateralized, which is the word that explains everything. You deposit, say, 150 dollars of ether into a lending contract, and it lets you borrow up to about 100 dollars of a stablecoin against it. If your collateral's price falls too far, the contract automatically sells it to repay the loan. That auto-sale is called liquidation, and it is merciless by design: no phone call, no grace period, executed by code the second the threshold hits.
Why would anyone borrow against more than they receive? Mostly to get spending money without selling an asset they expect to rise, or to make leveraged bets. Depositors on the other side earn the interest borrowers pay. Rates float with supply and demand, recalculated block by block. Aave and Compound are the long-running names.
What is a DEX and how do trades happen without a company?
A decentralized exchange, and the trick is called a liquidity pool. Instead of matching buyers with sellers, a contract holds a pot of two tokens, and a formula sets the price based on the pot's balance. Anyone can trade against the pot. Anyone can also deposit into the pot and earn a cut of trading fees, which is where the phrase yield farming comes from.
Uniswap made this model famous, and it is a genuine invention: a market that runs itself, permanently, with no operator to shut down. The cost is that pool depositors face impermanent loss, a quiet effect where the pool rebalances against you when prices move, and fees do not always cover it. Most people who farm yields never do that math.
Why do DeFi hacks happen so often?
Because the money sits in public code, and public code can be studied by every thief on earth until one finds the flaw. Bridge contracts, which move tokens between blockchains, have been the worst: the Ronin bridge lost about 620 million dollars in 2022, Poly Network over 600 million the year before. Flash loan attacks let someone borrow millions with no collateral for a few seconds, bend a protocol's prices with the borrowed weight, and pocket the difference, all inside one transaction.
Audits reduce the odds and eliminate nothing. A protocol that has run for years with big deposits has survived the most motivated code review in history, which is worth something. A protocol launched last month offering triple the yield has not.
Is DeFi safe for a normal person?
Treat it like the sharp end of an already sharp asset class. The honest checklist: use long-lived, heavily audited protocols rather than whatever a video promised; assume any yield far above the boring rate is being paid for a risk you have not identified yet; never put emergency money into a smart contract; and use a separate wallet for DeFi experiments so one bad approval cannot reach your savings.
The banks-without-bankers idea is not fake. Rules enforced by code, markets that never close, and loans that settle in seconds all work today. What DeFi removes along with the banker is the safety net, and the ledger does not care whether you understood the contract you signed.