I'm building a SaaS that accepts USDC payments. Simple requirement: customer sends stablecoins, I need to know when they arrived and the amount matches. Current options seem to be:

1. Payment processor (Coinbase Commerce, NOWPayments) — handles everything but takes 0.5-1% per transaction. On a $10k payment that's $50-100 just for confirmation.

2. DIY with Alchemy/Infura webhooks — poll for Transfer events, match amounts, track confirmations, handle reorgs, build retry logic. Took me ~2 weeks and it's still brittle.

Is there a middle ground? Something that just does the verification part — "tell me when X amount arrived at Y address" — without the custody/checkout/fee overhead? Curious how others are handling this, especially on L2s like Base where tx costs are negligible but verification infra is the same complexity as mainnet.