A swap interface that quotes honestly,
and an exchange backend that does not lose a fill
The number one complaint about a swap or exchange interface is a quote that was not the price the user actually got. We build the reconciliation underneath the screen first, slippage controls, fill tracking, a job that checks every balance against the chain, so the number shown is the number paid.
What it is and who needs it
A swap interface lets a user trade one token for another at a quoted rate; an exchange interface adds order tracking, fill history and, often, a path toward fiat. Both live or die on one thing: whether the rate shown is the rate the user actually gets, and whether every fill can be reconciled against the chain afterward. This is for a product adding token swaps to an existing wallet or app, or a team building a dedicated exchange front end on top of liquidity it does not need to provide itself.
What is inside
Quote aggregation across more than one liquidity source, so a rate is a comparison, not a single provider’s number taken on faith. Slippage limits and quote expiry the user sets, not a hidden default that works against them in a fast market. Order and fill tracking with a reconciliation worker that checks the resulting on-chain balance against what the fill record says happened, flagging any mismatch instead of letting it sit silently in a database. Hook points for KYC/AML if you work with a licensed partner, we do not provide licensed exchange services ourselves. An admin dashboard for volume, fee revenue and the small number of swaps that fail or need a manual look.
How we build it
We scope the token and chain list first, since aggregator coverage and gas economics vary enough between an EVM chain and something like Solana that it changes architecture decisions early. The quote and routing layer comes first and gets load-tested against a volatile market before any UI work, because a slow quote under load is where user trust breaks. Reconciliation is built in from the start, not bolted on after a support ticket about a missing balance, every fill writes a record that a background job verifies against the chain within minutes. We worked through this exact problem, pricing with margin and fee accounting, on our own multichain wallet and on exchange-adjacent project management for a crypto trading operation, and we carry those lessons into every build. We run the reconciliation job against a testnet environment under simulated load before any real liquidity touches the system, specifically checking what happens when a swap partially fills or a quote expires mid-transaction, the two failure modes that cause the most support tickets on a live exchange interface. A working demo ships every week during the build, so you can see real swaps executing on testnet rather than waiting until the end for a single reveal. We also document every assumption the routing logic makes about aggregator uptime, so a future outage at one liquidity source degrades the quote quality rather than breaking the interface outright.
Timeline and price
| Tier | Price | What it covers |
|---|---|---|
| MVP | from $6,000 | Core flow, one platform or chain, ready to test with real users |
| Production | from $14,000 | Full feature set, handover docs, agency keeps running it with you |
| Full control (handover-ready) | from $23,000 | Same scope, built and documented for your own team to run with zero dependency on us |
Timeline: 6 to 12 weeks for an MVP; production builds typically run longer depending on integrations.
What you own at the end
The full backend and client repository, in your own GitHub or GitLab organization. Order, fill and reconciliation data lives in a database you control, with export and backup documented in the handover. If you work with a licensed KYC/AML partner, that integration is yours to keep or change. Nothing in the architecture locks you to us for ongoing operation. We also hand over a written runbook for the reconciliation job itself, so your own engineers know exactly what it checks and how to extend it when a new liquidity source is added later.
Related
Part of our custom development work. See related builds: crypto wallet app, defi dashboard, token smart contract launch. On the technical side: crypto payments acceptance, crypto wallet integration. Related case study. Ready to scope yours? Get in touch and we will send back a written plan with a fixed price.
FAQ
How much does a swap or exchange interface cost?
A swap interface wired to one or two aggregators with basic slippage controls starts at $6,000. A fuller exchange with order tracking, admin tooling and fiat on/off-ramp hooks runs $14,000 and up, scoped after we see your target markets and whether you need a licensed KYC/AML partner.
How long does it take?
6 to 8 weeks for a swap interface MVP on a small set of chains and tokens. A production exchange with order book logic, reconciliation and admin tooling is 10 to 12 weeks.
What is the stack?
Node.js or Python/FastAPI backend, PostgreSQL for order and fill records, Redis for rate caching, aggregator APIs (1inch, Jupiter, 0x or similar depending on chain), Next.js or React Native for the client, and a reconciliation worker that polls chain state.
Who owns the exchange and its order data?
You. All order, fill and reconciliation data lives in your own database, and the repository is yours from day one. We never route your users' funds through infrastructure we control.
What support is included after launch?
30 days of fixes and tuning on the reconciliation job and quote routing, plus a written handover. Monitoring for stuck or failed swaps and adding new liquidity sources are available as ongoing work.