Day 21: Flash Loans and Uniswap Arbitrage: An Instantaneous Profit Play

Guilherme Soares
4 min readOct 21, 2023


Photo by Kostiantyn Li on Unsplash

“In a world where opportunities manifest in the blink of an eye, flash loans are the tools of the swift and the brave.” — DeFi Enthusiast

A Technical Dive: The Mechanics of Flash Loans

“In the world of blockchains, time and transactions are fluid; Flash loans make us question what’s possible within a single transaction.”


Flash loans have been a buzzword in the DeFi space. They revolutionized the way we think about loaning and borrowing in the blockchain universe. Instead of lengthy credit checks or collateral requirements, all you need is a smart contract and a strategy. But how does this work technically? Let’s plunge deep into the mechanics of flash loans.

The Basics of a Flash Loan

At its core, a flash loan is a type of loan that allows a user to borrow a specific amount of cryptocurrency without collateral on the condition that the loan is repaid within the same transaction block. If it’s not repaid, the transaction fails, and it’s as if it never happened.

How Are They Useful?

  1. Arbitrage: Spotting price discrepancies between DEXs, borrowing funds via a flash loan, executing trades, and then repaying the loan to make a profit.
  2. Collateral Swap: If you’ve deposited collateral in a platform and wish to change it without withdrawing, flash loans can facilitate this.
  3. Liquidations: If a user’s position is under-collateralized in a DeFi platform, it can be liquidated. With flash loans, users can source liquidity to do so.

What’s The Catch?

  1. Gas Fees: Everything must happen in a single transaction, which can be gas-intensive.
  2. Complexity: Creating a flash loan strategy requires a deep understanding of the DeFi ecosystem.
  3. Risks: If not executed properly, users can face unintended consequences or financial losses.




Guilherme Soares

I'm a senior software developer passionate about technology and to share knowledge.