# Building Stablecoin Payments at Scale | Justin Gainsley (Coinbase) at ETHConf

- Channel: [ETHGlobal](https://streameth.org/ethglobal)
- Date: 2026-07-09
- Duration: 14:52
- Topics: Coinbase, Justin Gainsley, ETHConf, stablecoin payments, Coinbase Commerce, USDC, Commerce Payments Protocol, escrow, smart contract, Base, auth and capture, Shopify, payment service providers, enterprise, interchange, Visa, Mastercard, Brian Armstrong, alternative payment method, operator, reclaim, settlement, reconciliation, disputes, gas fees, on-ramps, wallets, signing UX, smart wallets, fiat settlement, compliance, digital dollars, savers, checkout, memecoins, crypto payments
- Watch: https://streameth.org/watch/yt-etDIkNGqneA
- YouTube: https://www.youtube.com/watch?v=etDIkNGqneA

## Description

In this talk, Justin Gainsley, who leads stablecoin payment acceptance at Coinbase, shares what four years of building stablecoin payments at scale has taught him about selling to enterprises and payment service providers, and what still needs to be accomplished. He opens with a 2012 Hacker News post from Coinbase founder Brian Armstrong, written before he even applied to Y Combinator, expressing the idea of using crypto to remove the 2 to 3% interchange tax Visa and Mastercard charge on every payment, showing crypto as a payment method has been ingrained in Coinbase from the start. Taking over Coinbase Commerce with the same mandate, Justin's team tried nearly everything (Bitcoin payments, every token on every chain, memecoins, cashback, point of sale, invoicing, online checkout) but nothing moved the needle, and for a while they worried crypto might not be right for payments.

The signal emerged from talking to hundreds of buyers and merchants: a real cohort wanted crypto as their cash, something stable to earn into and spend without gas or volatility. So Coinbase made the non-consensus bet of stripping out Bitcoin, Ethereum, and all volatile assets to go all in on stablecoins, which drew internal backlash but sent conversion, volume, and merchant satisfaction all up. Strikingly, 64% of wallets paying on the stablecoin only product held no other assets, a fundamentally new cohort of savers rather than traders. Justin recounts bringing what they thought was the industry's best stablecoin checkout to Shopify, only to be asked about auth and capture, a term he had never heard, kicking off a year of learning what a real payment system requires: authorization holds, automated voids, configurable expiries, refunds, settlement schemes, reconciliation, and disputes. He details the resulting open source Commerce Payments Protocol, an escrow smart contract on Base powering Shopify's USDC checkout across hundreds of thousands of sites, with a permissionless operator role, six operations (authorize, capture, charge, void, refund, reclaim), and a blockchain native reclaim function letting buyers pull funds back after expiry. He covers the boring but required enterprise needs (predictable flat gas fees, custom settlement files, daily fiat delivery, compliance), argues the blockchain itself is fine for payments since Base settles in 200 milliseconds for under a penny, and identifies wallets, on-ramps, and signing UX as the real problems. He closes noting stablecoin payments have gone from curiosity to production in two years.

00:00 Introduction
00:41 Brian Armstrong's 2012 Post on Removing Interchange
01:09 Why Crypto Payments Are in Coinbase's DNA
01:35 Trying Everything to Make Crypto Payments Work
02:00 Worrying Crypto Might Not Fit Payments
02:23 Listening Closely to Buyers and Merchants
02:41 The Camp That Wanted Crypto as Cash
03:06 The Non-Consensus Bet on Stablecoins
03:35 The Internal Backlash
03:58 Why All the Metrics Went Up
04:28 64% of Wallets Held No Other Assets
04:54 The New Cohort of Savers
05:14 Bringing the Best Checkout to Shopify
05:32 The Auth and Capture Question
06:08 A Year Learning What Payments Require
06:32 Why Not to Underestimate Traditional Payments
07:15 Plugging Into Where Enterprises Already Are
07:37 The Commerce Payments Protocol on Base
08:01 How the Escrow Smart Contract Works
08:28 The Operator Role Explained
08:46 Why Operators Cannot Modify or Lock Funds
09:28 The Six Core Operations
09:48 Reclaim as a Blockchain Native Feature
10:12 The Boring but Required Enterprise Needs
10:33 Predictable Flat Gas Fees
10:44 Custom Settlement Files per PSP
11:01 Daily Fiat Delivery and Compliance
11:26 Just Another Alternative Payment Method
11:54 What the Industry Still Needs
12:19 Why the Blockchain Is Fine for Payments
12:42 Where Wallet UX Kills Conversion
13:03 Why On-Ramps Still Need to Be Better
13:27 Signing UX and Smart Wallet Adoption
13:59 From Curiosity to Production in Two Years
14:41 Closing

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