Karta is building its self-custody money app on Tempo

Karta, a self-custody money app with more than 25,000 monthly cardholders and 1,250+ business teams across 150+ countries, is building on Tempo. Karta's treasury is live on Tempo today, and Karta Personal launches on Tempo soon.

“At Karta, self-custody isn't a feature, it's the architecture. Every user holds their own stablecoin balance on their own wallet, and every transaction they make settles on-chain. Doing that at consumer scale was only possible on infrastructure built for payments, not retrofitted for them. Tempo is the first chain where we didn't have to trade self-custody for a product that actually works.”

Nik ZimarkovCo-founder and CEO, Karta

About Karta

Karta is a self-custody money app. Its product includes a Visa card accepted in 150+ countries, fiat virtual accounts in the US today with expansion underway globally, and a wallet for cross-currency earning, spending, and sending. Karta is live on Telegram, with iOS and Android rolling out, and reports 25,000+ monthly cardholders and 1,250+ business teams.

Karta's partner stack is Privy for self-custody wallets, Bridge for fiat rails and virtual accounts, and Tempo for settlement.

The problem Karta set out to solve

Karta describes its challenge as four payment-infrastructure constraints that converge when building self-custody payments at consumer scale.

• Gas. Every transaction on a general-purpose chain requires a native gas token, which users of a consumer money app would have to acquire before moving the asset they actually care about.
• Signing. In a pure self-custodial model, every transaction requires a live signature from the wallet owner, which makes real-time asynchronous flows like card authorizations structurally difficult.
• Finality as a fraud surface. Seconds-long finality creates windows for double-spend attempts that millisecond-level card authorization cannot tolerate.
• Metadata and reconciliation. Partner rails depend on per-transaction context such as invoice references and compliance flags. Rebuilding that from event logs adds cost and fragility.

What Karta is building on Tempo

Karta's treasury is live on Tempo today. Karta Personal, Karta's consumer product, launches on Tempo soon, alongside fiat virtual account expansion to new markets. Karta Business migrates onto the same settlement layer shortly after.

Per Karta, its consumer architecture is structured as follows: a self-custodial smart account is provisioned on Tempo via Privy, USD balances are held as USDC on that account, and card authorizations settle against the on-chain balance inside standard card authorization windows.

Why Karta chose Tempo

Each of the constraints above has been solved individually on different chains. Paymaster contracts handle gas abstraction. Account abstraction and session keys approximate asynchronous signing. Emerging rollups approach sub-second finality. Specialty payment chains expose structured metadata. Tempo's architecture consolidates each of them into native protocol capabilities.

• Sub-second deterministic finality. Transactions finalize on-chain in approximately 500ms with no re-orgs, inside standard card authorization windows.
• Stablecoin-native gas. Gas is paid in USD stablecoins at the protocol level. No native gas token, no paymaster contracts, no ERC-4337 retrofits.
• Access Keys. A protocol-level primitive for authorized debits against a wallet without custody transfer. Card authorizations can settle asynchronously against an on-chain balance without a live wallet signature at authorization time.
• Dedicated payment lanes. Payment traffic has guaranteed blockspace at the protocol level, insulated from unrelated network activity.
• Structured memo fields. Native per-transfer metadata, ISO 20022-compatible, supports reconciliation and compliance workflows.

“Each of these problems has a workaround somewhere: paymasters for gas, session keys for signing, rollups for finality. But they live on different chains and in different retrofits, and shipping a consumer product at mainstream scale means solving all of them on the same stack. Tempo is the first chain where each one is a first-class protocol feature rather than a workaround bolted onto a general-purpose VM. That's the difference between the full payment path living on-chain and an off-chain ledger reconciled after the fact.”

Matt AlievCo-founder and CTO, Karta

What's ahead

Karta Personal launches on Tempo soon, with fiat virtual account expansion to new markets following close behind. Karta Business migrates onto the same settlement layer shortly after.

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