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. The number shown has to be the number paid.
The one thing users actually complain about
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 the same thing: is the rate shown the rate the user actually gets, and can every fill be checked against the chain afterward.
This fits a product adding token swaps to an existing wallet or app. It also fits a team building a dedicated exchange front end on top of liquidity it does not need to provide itself.
What is inside
Quotes get aggregated across more than one liquidity source, so a rate is a comparison, not one provider’s number taken on faith. Slippage limits and quote expiry are set by the user, not a hidden default working against them in a fast market.
Order and fill tracking runs through a reconciliation worker that checks the resulting on-chain balance against what the fill record claims. Any mismatch gets flagged, not left to sit silently in a database. We add hook points for KYC/AML where you work with a licensed partner. We do not provide licensed exchange services ourselves. An admin dashboard covers 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. Aggregator coverage and gas economics vary enough between an EVM chain and something like Solana that it changes early architecture decisions. The quote and routing layer comes before any UI work, and gets load-tested against a volatile market. A slow quote under load is exactly where user trust breaks.
Reconciliation is built in from the start, never bolted on after a support ticket about a missing balance. Every fill writes a record, and a background job verifies it 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. Those lessons carry into every build.
We run the reconciliation job against a testnet environment under simulated load before any real liquidity touches the system. We specifically check two failure modes: a swap that partially fills, and a quote that expires mid-transaction. Those two cause the most support tickets on a live exchange interface. A working demo ships every week during the build, so you see real swaps executing on testnet rather than waiting for one reveal at the end. We also document every assumption the routing logic makes about aggregator uptime, so an outage at one liquidity source degrades quote quality instead of 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, support available as ongoing work |
| Full control (handover-ready) | from $15,000 | 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 sit 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. Your own engineers see exactly what it checks and how to extend it when a new liquidity source gets 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. We scope it after seeing 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 such as 1inch, Jupiter or 0x, 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 do. All order, fill and reconciliation data lives in your own database. The repository is yours on payment, as set in the contract, with read access 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.