Ethereum

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What is L2?

Rollup?

Smart Contracts

https://ethereum.org/en/developers/tutorials/

Intro

Smart contracts are a type of Ethereum account. This means they have a balance and they can send transactions over the network. However they're not controlled by a user, instead they are deployed to the network and run as programmed. User accounts can then interact with a smart contract by submitting transactions that execute a function defined on the smart contract. Smart contracts can define rules, like a regular contract, and automatically enforce them via the code.

High gas costs? Should check how expensive…

Smart contracts alone cannot get information about "real-world" events because they can't send HTTP requests. This is by design as relying on external information could jeopardise consensus, which is important for security and decentralization.

Languages

https://ethereum.org/en/developers/docs/smart-contracts/languages/

Solidity: https://solidity.readthedocs.io/en/v0.7.4/
Vyper: https://vyper.readthedocs.io/en/stable/

more advanced: Yul, intermediate to the EVM cheatsheet Solidity vs Vyper: https://reference.auditless.com/cheatsheet/

Anatomy

https://ethereum.org/en/developers/docs/smart-contracts/anatomy/

Storage: permanently in the blockchain, expensive
Memory: only stored during the contract's execution, cheaper
Env var: block timestamp, msg.sender…
Functions: internal (only accessible internally) vs external (can be called from other contracts and through transactions)
public vs private for both functions and values?
view functions: "getter" function not modifying state
constructor functions: to initiate the state, only ran at contract creation
built-in functions: address.send()
ERCs: set of standards

https://ethereum.org/en/developers/docs/security/

Resources

Tutorials

https://ethereum.org/en/developers/tutorials/ https://learnxinyminutes.com/docs/solidity/

Interactive Tutorials

https://cryptozombies.io/ https://ethernaut.openzeppelin.com/

Infrastructure

https://infura.io/: Ethereum node; have account and keys (acquired by ConsenSys, Feb 2026) https://dashboard.alchemy.com/: Ethereum node; have account (legacy alchemyapi.io retired Jan 2026)

Local Dev Env

https://ethereum.org/en/developers/local-environment/ https://hardhat.org/ compile, deploy, test, and debug your Ethereum software (Hardhat 3 in dev, 2026) ~~https://openzeppelin.com/sdk/ interacting with smart contracts in the CLI~~ deprecated, superseded by OpenZeppelin Upgrades Plugins ~~https://www.trufflesuite.com/ tools for smart contracts~~ / ~~https://www.trufflesuite.com/ganache local copy of an Ethereum blockchain~~ discontinued by ConsenSys, Sept 2023, repos archived Feb 2024 — use Hardhat/Foundry instead ~~https://framework.embarklabs.io/ all-in-one for dapps~~ effectively inactive, no maintenance ~~https://eth-brownie.readthedocs.io/en/stable/deploy.html Python-based, better than the rest?~~ unmaintained, use Ape Framework instead

Foundry

https://onbjerg.github.io/foundry-book/index.html forge init {project} to start a new project

Misc

https://github.com/tintinweb/smart-contract-sanctuary lists all smart contracts on Etherscan? https://twitter.com/zapper_fi/status/1327035284677128192?s=09 explain why "Approve DAI", "Enable USDC"

Technical Notes

Ethereum accounts

https://ethereum.org/en/developers/docs/accounts/#an-account-examined

Ethereum accounts have four fields:

nonce – a counter that indicates the number of transactions sent from the account. This ensures transactions are only processed once. If a contract account, this number represents the number of contracts created by the account
balance – the number of Wei owned by this address. Wei is a denomination of ETH and there are 1e+18 Wei per ETH.
codeHash – All such code fragments are contained in the state database under their corresponding hashes for later retrieval. For contract accounts, this is the code that gets hashed and stored as the codeHash. For externally owned accounts, the codeHash field is the hash of the empty string.
storageRoot – A 256-bit hash of the root node of a Merkle Patricia tree that encodes the storage contents of the account (a mapping between 256-bit integer values), encoded into the trie as a mapping from the Keccak 256-bit hash of the 256-bit integer keys to the RLP-encoded 256-bit integer values. This tree encodes the hash of the storage contents of this account, and is empty by default.

Your private key is what you use to sign transactions, so it grants you custody over the funds associated with your account. You never really hold cryptocurrency, you hold private keys – the funds are always on Ethereum's ledger.

Ethereum clients

https://ethereum.org/en/developers/docs/nodes-and-clients/#clients GETH: https://geth.ethereum.org/docs/ Go's Ethereum implementation OpenEthereum: https://github.com/openethereum/openethereum Rust Trinity: https://trinity.ethereum.org/ Python

Ethereum transactions

https://ethereum.org/en/developers/docs/transactions/#whats-a-transaction

A submitted transaction includes the following information:

recipient – the receiving address (if an externally-owned account, the transaction will transfer value. If a contract account, the transaction will execute the contract code)
signature – the identifier of the sender. This is generated when the sender's private key signs the transaction and confirms the sender has authorised this transaction
value – amount of ETH to transfer from sender to recipient (in WEI, a denomination of ETH)
data – optional field to include arbitrary data
gasLimit – the maximum amount of gas units that can be consumed by the transaction. Units of gas represent computational steps
gasPrice – the fee the sender pays per unit of gas

Ethereum node types

https://ethereum.org/en/developers/docs/nodes-and-clients/#node-types

In fact, clients can run 3 different types of node - light, full and archive. There are also options of different sync strategies which enables faster synchronization time. Synchronization refers to how quickly it can get the most up-to-date information on Ethereum's state.

Full node

Stores full blockchain data.
Participates in block validation, verifies all blocks and states.
All states can be derived from a full node.
Serves the network and provides data on request.

Light node

Stores the header chain and requests everything else.
Can verify the validity of the data against the state roots in the block headers.
Useful for low capacity devices, such as embedded devices or mobile phones, which can't afford to store gigabytes of blockchain data.

Archive node

Stores everything kept in the full node and builds an archive of historical states. Needed if you want to query something like an account balance at block #4,000,000.
These data represent units of terabytes which makes archive nodes less attractive for average users but can be handy for services like block explorers, wallet vendors, and chain analytics.

Proto-Danksharding

https://notes.ethereum.org/@vbuterin/proto_danksharding_faq

Protocols

Lending

https://compound.finance https://app.aave.com

DEXs (Decentralized Exchanges)

AMM

Uniswap

V1

ERC20 <> ETH

V2

ERC20 <> ERC20

V3

Can add single assets as liquidity Will use a Layer-2

Concentraded liquidity

Will be possible to concentrade liquidity in a specific range

Non-fungible liquidity

LP tokens won't be ERC20 anymore but ERC721 Trading fees no longer automatically reinvested

Flexible fees

0.05% => Stablecoins pairs 0.3% => Standard pairs 1% => Exotic pairs

Oracle

TWAP past 9 days on-chain

Pricing LP positions

https://lambert-guillaume.medium.com/pricing-uniswap-v3-lp-positions-towards-a-new-options-paradigm-dce3e3b50125

Arbitrage

https://github.com/ccyanxyz/uniswap-arbitrage-analysis https://github.com/libevm/subway

Sushiswap

Survived a near-collapse; new leadership took over Dec 2025, token down ~99% from ATH

Balancer

Hit by a $110-128M exploit (Nov 2025); the corporate entity behind it shut down in March 2026 citing legal exposure. Protocol/DAO continuing in some form.

Kyberswap

Repeatedly hacked ($47M in 2023, tied to an ~$80-100M USR exploit in 2026); aggregator still operating

0x

for stablecoins

Curve

AMM for stablecoins

Orderbook-based

dYdX

L2

Everything is done on L2 No gas fees once coins are deposited on L2 From time to time, L2 is synced to L1

Deversifi => rhino.fi

Rebranded to rhino.fi in July 2022; still operating as a multi-chain L2 DeFi gateway https://rhino.fi

Lighter

https://lighter.xyz

Aggregators

"Hedge Funds"

Yearn

Automated on-chain hedge fund https://yearn.finance

Stake DAO

https://stakedao.org/

Harvest Finance

https://harvest.finance

Keeper DAO => Rook

Rebranded to Rook (ROOK); original KeeperDAO brand discontinued

Formation.fi

https://formation.fi/ Yield farming optimizer

Derivates

https://synthetix.io

Options

Hegic

https://hegic.co

Pods

https://www.pods.finance/

Perpetual Futures

Cap

https://cap.io/

DECENTRALIZED PERPS Trade global markets with low fees, deep liquidity, and up to 100× leverage.

On Arbitrum L2 Status as of 2026 unclear/ambiguous (name conflated with other "Cap" projects)

Alchemix

https://app.alchemix.fi/ Deposit DAI, borrow up to 50% as alUSD Yield on DAI through YFI pays back the loan itself

sideshift

https://sideshift.ai/btc/eth Not sure I understand the appeal?

Fei

New algo stablecoin

<2021-04-07> update: looks like Fei failed miserably… https://rekt.news/fei-rekt/ Confirmed defunct: merged into Tribe DAO, wound down starting Aug 2022 after the $80M Rari/Fuse hack

APWine => Spectra Finance

Rebranded to Spectra Finance (July 2023); relaunched June 2024, active (~$20M TVL) https://www.spectra.finance/

TimeSwap

"Like Uniswap, but for lending & borrowing" https://app.timeswap.io/ Faded: token has effectively stopped trading on major exchanges

Euler

https://www.euler.finance/#/ Hacked for ~$200M in March 2023 (100% recovered); relaunched as Euler v2, TVL hit an all-time high by 2026

Other Projects

https://zapper.fi: portfolio management. Shutting down Aug 3, 2026 — site/apps/API closing after 7 years https://feed.chain.link: on-chain price reference data https://defirate.com & https://yieldfarming.info: yield rate comparison https://tornado.cash: anonymize ETH transactions. OFAC lifted sanctions March 2025 (Fifth Circuit ruled immutable contracts aren't sanctionable "property"); co-founder Alexey Pertsev separately convicted of money laundering in the Netherlands, May 2024

Flash Loans

AAVE, ~~dYdX~~, Uniswap… Balancer V2: https://twitter.com/fcmartinelli/status/1461777136071716875

Resources

https://defiprime.com/flahloans-comparison https://money-legos.studydefi.com/#/dydx https://github.com/fifikobayashi this guy have some repos using flash loans

Flash Mints

https://docs.makerdao.com/smart-contract-modules/flash-mint-module

MEV

Miner Extracted Value https://www.coindesk.com/ethereum-trading-bot-strategy-miner-extracted-value-research

One can look at the waiting transactions on the Ethereum blockchains and upbid "profitable" transactions so it executes faster.

Flashbots

https://docs.flashbots.net/

Resources

https://noxx.substack.com/p/dex-arbitrage-mathematical-optimisations

Resources

https://www.libevm.com/

Ethereum

What is L2?

Smart Contracts

Intro

Languages

Anatomy

Resources

Tutorials

Interactive Tutorials

Infrastructure

Local Dev Env

Foundry

Misc

Technical Notes

Ethereum accounts

Ethereum clients

Ethereum transactions

Ethereum node types

Full node

Light node

Archive node

Proto-Danksharding

Protocols

Lending

DEXs (Decentralized Exchanges)

AMM

Uniswap

V1

V2

V3

Arbitrage

Sushiswap

Balancer

Kyberswap

0x

for stablecoins

Curve

Orderbook-based

dYdX

L2

Deversifi => rhino.fi

Lighter

Aggregators

1inch

Matcha

Dex.guru

"Hedge Funds"

Yearn

Stake DAO

Harvest Finance

Keeper DAO => Rook

Formation.fi

Derivates

Options

Hegic

Pods

Perpetual Futures

Cap

Alchemix

sideshift

Fei

APWine => Spectra Finance

TimeSwap

Euler

Other Projects

Flash Loans

Resources

Flash Mints

MEV

Flashbots

Resources

Resources