SwiftandScale
12 years building custom software
SaaS development services for a product sold to many customers: sign-up, a workspace each customer sees alone, payment through your provider, and the journey they pay for. Ten weeks, tests in the price.
“We invoice our first three customers by hand, and renewals live in a calendar.”
Right for the start: the first forgotten renewal is revenue nobody sees leave.
“The prototype works for one customer. The second needs its own login, its own data and a different plan.”
That is when a tool becomes a product, and who sees what lives in the data.
“We were quoted for billing as one line, and nobody could say what happens when a card fails.”
Billing is not the checkout page. It is the failed renewal, the downgrade and the refund — the part a demo never shows.
SaaS product development usually fails in one order: the dashboard first, billing and isolation last. We build it the other way round — that is where SaaS web development stops being a boilerplate.
| Journey | First ten weeks | Phase two | Not us |
|---|---|---|---|
| Sign-up and the first ten minutesAn empty workspace has to explain itself to a stranger. | Covered · First ten weeks | Not covered · Phase two | Not covered · Not us |
| A workspace each customer sees aloneThe customer is part of every query, and a test proves it. | Covered · First ten weeks | Not covered · Phase two | Not covered · Not us |
| Plans and payment through your providerThe account follows the provider’s events, not the success page. | Covered · First ten weeks | Not covered · Phase two | Not covered · Not us |
| The one journey customers pay forThe reason anyone signs up. | Covered · First ten weeks | Not covered · Phase two | Not covered · Not us |
| Usage credits, if you charge by useOnly when pricing is metered. Then it is a ledger, never a counter. | Covered · First ten weeks | Not covered · Phase two | Not covered · Not us |
| An admin side for youWho pays, who is stuck, and a switch for a paid feature. | Covered · First ten weeks | Not covered · Phase two | Not covered · Not us |
| Single sign-on and audit logsWhen a larger customer asks for it in a contract, not before. | Not covered · First ten weeks | Covered · Phase two | Not covered · Not us |
| A mobile app on the same accountsThe natural next stage: same team, same data, both stores. | Not covered · First ten weeks | Covered · Phase two | Not covered · Not us |
| Holding card dataThe payment provider does that, under your contract. | Not covered · First ten weeks | Not covered · Phase two | Covered · Not us |
When the budget is tighter, we say what waits. Money and data always go first.
Hiding another customer’s records in the interface is not isolation; leaving them out of the query is. Every path that returns data gets a test asking for someone else’s record and expecting a refusal — our marketplace has exactly that test, answered with a 403. SaaS application development is mostly this discipline, repeated on every screen.
Access decided by four dimensions at onceThe browser may close before the payment page reports back. So an account changes plan when the provider tells the server, not when a screen says success, and repeated or out-of-order events are normal traffic. That is the rule we build billing to, and its tests replay the repeated event as well as the first.
How we build the money paths of a marketplaceOur marketplace meters its AI studio in credits. Each generation is debited inside one database transaction, with the balance condition in the update itself, so two clicks cannot spend one credit twice; every movement is a typed ledger row, and a failed generation refunds with its own entry.
The AI studio billed by the generationWhen customers open the product several times a week, an app earns its place. Mobile apps are our specialisation: the same team builds it on the same accounts and billing, for both stores, quoted separately.
Mobile app development: one journey, both stores, eight weeksEvery week ends in something you can sign up to and click through, not in a document.
Who signs up and how they pay: per seat, per month or by use.
You seeThe agreed scope and a staging address that answers.
Accounts, invitations, roles and the workspace boundary, with its tests.
You seeYou sign up as two customers, and neither can see the other.
The core of the product, end to end.
You seeThe journey works inside a workspace, failures included.
Plans, trial, upgrade, the failed renewal and the downgrade after it.
You seeA test card upgrades a workspace; a declined one downgrades it.
Real users try to break it; then production moves to your accounts.
You seeA live product, deployed once by your own developer.
Quoted from real usage. Often it is the mobile app.
You seeA decision made on usage, not on opinion.
Both come from the repository of our own marketplace. Real output, not a mock-up.
Fourteen tests over the AI studio: a debit written to the ledger, a refusal when credits run out, another brand’s project answered with a 403.
Listed from test/ai-studio.e2e-spec.ts in ugc.backend, 8 October 2026.
Twenty-four suites, 173 passed, two skipped, warnings left in.
jest over test/*.e2e-spec.ts in ugc.backend, 21 August 2026
A SaaS development agency that says yes to everything is guessing; if the honest answer is no, you hear it on the first call.
Short answers. The long ones happen on the call.
Neither is a subscription product, and we will not pretend otherwise; each carries one of the two hard parts. Both demos open on sample data.
A marketplace with two sides, a payment held between them, and an AI studio that bills by the generation. The hard part is never the catalogue — it is deciding, in code, the exact moment money and files change hands.
Usage tied to what an account may do: an AI studio metered in credits, a ledger under them, 173 end-to-end tests over the product.
Made-to-order production has no catalogue and no reorder button. Every item is built for one person from measurements a computer takes off a scan, and the system has to hold that thread from the first appointment through manufacturing, delivery, and the remake eighteen months later.
Data that stays with its owner: access decided by brand, branch, city and legal entity at once.
The final invoice is paid, the call happens, the access is transferred. Six months later nobody can deploy. Handover is a process, not a meeting, and it is the cheapest insurance in a project.
Most clients assume paying for a build means owning it. Usually true of the code, and often false of everything the code needs in order to run.
Everyone agrees on starting small and nobody agrees on how small. The rule that has worked for us: one journey, all the way through, including its bad days.