Shares of Square, the increasingly bank-like tech company run by part-time Twitter CEO Jack Dorsey, have been on a blistering run over the past year, gaining more than 200%.

The stock was soaring even before the news in November that Square Cash app users would be able to buy and sell bitcoin; this week, it blew past those earlier highs and set a series of new records. The company’s growth has also been powered by bank partnerships that perhaps resemble what JPMorgan and Amazon (paywall) are reportedly considering.

The San Francisco-based firm is best known for its card-payment dongle, but it does a lot of other things, too. Square Capital lent out $305 million to small businesses in the fourth quarter (pdf), and the company also provides a suite of services for retailers like inventory tracking and accounting. Offering bitcoin, meanwhile, can be great way to attract new customers, especially considering most major banks are still afraid to touch it. The Square Cash payment app had more than 7 million monthly active users in December.

Eye-popping gains can be easier when you start out small, and Square is still tiny compared to payment companies like PayPal, which has a market capitalization that’s almost five times bigger. Dorsey’s company had $17.9 billion of gross payment volume in the fourth quarter, compared with $131 billion in total payment volume for PayPal. Despite its larger size, PayPal’s payment volume grew slightly faster over the past year, at 32%, versus Square’s 31%.

Numbers aside, Square Cash works a lot like a checking account. Users can receive direct deposits from their employers and withdraw money from ATMs using its Cash Card, which is essentially a pre-paid card in partnership with Sutton Bank. ”These features provide customers who may not have access to traditional financial services with an easy way to store and access their money,” Square said in its shareholder letter.

This resembles the discussions that are taking place between Amazon and large banks like JPMorgan and Capital One, according to the Wall Street Journal (pdf). A “checking-account-like product” backed by the online retailer is reportedly meant to attract customers without bank accounts and younger clientele. JPMorgan CEO Jamie Dimon declined to confirm the talks during a recent interview with Bloomberg, but he praised Amazon as a partner and said the bank already dominates when it comes to millennials.

While Amazon has terrified whole industry segments when it targets them, finance is thought to be relatively protected by thickets of regulation. If they want to be in financial services, tech companies may prefer partnerships to outright acquisitions or building their own digital banks.

Even so, companies like Square are getting awfully close to the banks’ turf. If they surmount some formidable obstacles, the banks risk becoming undifferentiated, low-margin utilities running in the background. Big tech groups like Amazon and Google are often seen as the most dangerous potential competitors to traditional banks, but Square’s progress suggests that smaller companies with ambitious plans can make inroads too.