Today I saw a bunch of screenshots of "risk-free arbitrage" on the blockchain again.

Honestly, what you see as an opportunity, others see as your transaction fee.
Sandwich attacks are even more annoying; just after you make a move, thinking you've caught a misprice, a slippage pulls the price apart, and your profit turns into a tip for someone else...
Now I’d rather do two fewer trades, and first check the pool depth and whether the recent transactions involve "the same group of people" moving back and forth.
Layer 2 has been comparing TPS, fees, and subsidies lately—it's lively, but the more "cheap + fast" environments there are, the more they favor those quick-handed bots.
Anyway, I take simplicity as a trap: when I see "just move some assets around to make money," I first think someone is waiting for you to enter.
For now, that’s it, I’ll review it later.