PetarStoev02How Transactions Work
A transaction is a signed instruction to change state on the blockchain. Every token transfer, contract call, and NFT mint is a transaction.
The lifecycle of a transaction
1. Build
Your dApp constructs the transaction — what to do, who's involved, how much to pay.
2. Sign
Your wallet signs the transaction with your private key. This proves you authorized it without revealing the key.
3. Broadcast
The signed transaction is sent to the network (via an RPC node).
4. Include
A validator picks up your transaction and includes it in a block.
5. Confirm
The block is added to the chain. Your transaction is now part of the permanent record.
EVM transactions
An EVM transaction contains:
| Field | Purpose |
|---|---|
from | Your address (derived from signature) |
to | Recipient address (or contract address) |
value | Amount of native ETH to send |
data | Encoded function call (for contract interactions) |
gasLimit | Maximum gas you're willing to use |
maxFeePerGas | Maximum price per unit of gas |
maxPriorityFeePerGas | Tip for the validator |
nonce | Sequential counter preventing replay attacks |
chainId | Which chain this transaction is for |
Gas explained
Gas is the unit of computational work on EVM chains. Every operation costs gas:
- Sending ETH: 21,000 gas
- ERC-20 transfer: ~65,000 gas
- Uniswap swap: ~150,000 gas
You pay: gasUsed × gasPrice in the chain's native token.
Gas price fluctuates based on network demand. On Ethereum mainnet, a simple transfer might cost $0.50-$5. On L2s (Arbitrum, Base), the same transfer costs $0.01-$0.10.
Solana transactions
A Solana transaction contains:
| Field | Purpose |
|---|---|
instructions | Array of operations to execute (can be multiple) |
recentBlockhash | Proves the transaction is recent (expires after ~60 seconds) |
signatures | One or more signatures from required signers |
Instructions
Each instruction specifies:
- Program ID — which on-chain program to call
- Accounts — which accounts the instruction reads/writes
- Data — the instruction payload
Key difference: Atomicity
A Solana transaction can contain multiple instructions that all execute atomically — all succeed or all fail. On EVM, each transaction is a single operation (though contracts can batch internally).
// Solana: one transaction, three instructions
Transaction([
createTokenAccount(...),
transferTokens(...),
closeEmptyAccount(...)
])
// All three happen atomically
Fees
| EVM | Solana | |
|---|---|---|
| Model | Variable gas price × gas used | Fixed base fee (5,000 lamports per signature) + optional priority fee |
| Cost | $0.01 (L2) to $50+ (Ethereum mainnet) | ~$0.0005 per transaction |
| Predictability | Unpredictable — depends on network congestion | Very predictable |
| Who pays | Sender always pays gas | Sender pays, but programs can subsidize |
Confirmation and finality
EVM (Ethereum):
- 1 confirmation = included in a block (~12 seconds)
- 12+ confirmations = considered "final" (~2.5 minutes)
- Blocks can be reorganized (reorged) — wait for enough confirmations for valuable transactions
Solana:
processed— seen by the connected validatorconfirmed— voted on by supermajority of validators (~400ms)finalized— rooted, extremely unlikely to be reverted (~6 seconds)
For most dApp interactions, confirmed on Solana and 1-3 confirmations on EVM are sufficient.
Failed transactions
EVM: If a transaction fails (contract reverts, out of gas), you still pay gas fees. The gas was used to compute that the transaction should fail.
Solana: If a transaction fails, you still pay the base fee (5,000 lamports). But since fees are tiny, failed transactions are cheap.
Common failure reasons:
- Insufficient balance
- Contract revert (logic error, failed require)
- Expired transaction (Solana: blockhash too old)
- Gas too low (EVM: transaction runs out of gas)
- Nonce mismatch (EVM: transactions must be sequential)