SaaS development in London
Selling software to a London bank or insurer means meeting an enterprise buyer's expectations before anyone looks at your features. Their IT team wants single sign-on, roles that match their organisation, activity logs they can export, tenant isolation and backups that restore, and a SaaS product built for startups usually covers half of that. They will ask how you fail as well as how you work.
We build the parts that make a SaaS product ready for those customers: SAML and OIDC sign-on, role models that survive the first enterprise contract, activity logs the customer can export, and data isolation that is enforced in the database rather than trusted to the application. Every answer you give the buyer is then backed by working code.
Financial services drive more of London's software demand than any other sector. Payments companies, challenger banks, wealth platforms and brokers need ledgers that reconcile, APIs that stay correct when a partner retries, and apps customers trust with their money. Most of them reached the market fast, which was the right call at the time, and now run systems built for launch rather than for the size they have become. The work is making those systems dependable without stopping the business that runs on them.
Insurance is its own case. The specialty insurers, managing agents and brokers around Lloyd's still run much of their work on ageing policy administration platforms and spreadsheets that travel between firms by email. Lloyd's has moved away from Blueprint Two, the market-wide programme that was meant to digitise placement and claims, so each firm is modernising its own systems one integration at a time. The City's law firms and consultancies sit alongside them, holding decades of documents and few ways to search them by meaning.
Media, retail and the public sector bring different problems. Publishers run subscriptions, paywalls and content systems that have to hold up on a busy news day. Direct-to-consumer brands outgrow their first shop as they start selling into Europe and the US. Suppliers to councils and NHS bodies build services that have to work for every resident, including people using a keyboard or a screen reader. Hiring is the common constraint. ITJobsWatch puts the median advertised salary for a software engineer in London at £98,750 over the six months to September 2026, and banks, fintechs and the large technology firms compete for the same people.
Working with us from London is straightforward. Four hours of every working day overlap with yours, set across your morning, so stand-up, code review and the decisions that follow happen live. You talk to the engineer who writes the code, in your own Slack, GitHub and Linear. The rest of the day moves forward in pull requests you can read at your desk, with runbooks and architecture notes written as the work goes.
We are the right fit when you have a defined piece of work and need senior engineers on it this month rather than next quarter. Start with a fixed-price two-week piece and judge us on what ships. We add capacity while a London hire is still in progress, and we work white-label under your name for agencies.
Four ways this arrives.
Then SCIM, then role mapping, then a security questionnaire. We add SAML and OIDC through a provider or your own identity stack, provision users from their directory, and keep the permission model working for the self-serve customers who never asked for any of it.
Shared tables with a tenant column and every query trusted to filter on it. We enforce isolation below the application, with Postgres row-level security or separate schemas, and write tests that try to read across tenants and must fail.
Moving from seats to usage, adding a free tier, or selling annual contracts beside monthly plans. We model plans and entitlements separately from the payment provider, meter usage into a ledger you can audit, and make proration and dunning tested code rather than a monthly surprise.
Every larger customer asks who changed what, who can reach production and how access ends when someone leaves. We build exportable audit logs, least-privilege access and change control through pull requests, so your answer is a screen, not a spreadsheet.
A multi-tenant platform scoped per organisation, with admin screens for users, access and login alerts, and a way for an administrator to view the app as any user.
Read the write-up →Asked by London teams.
How do you work with teams in London?+
Four hours of every working day overlap with yours, set across your London morning, so stand-up and code review happen live. We join your calls and work in your tools: Slack, GitHub and Linear. You talk directly to the engineer who writes the code. Outside the overlap, the work carries on in pull requests you can read at your desk, and runbooks and architecture notes are written as we go.
Do you build for London fintechs and insurers?+
Yes. For payments companies, challenger banks and wealth platforms we build ledgers that reconcile, webhook handling that stays correct when a provider retries, and React Native apps with biometric sign-in and step-up checks for risky payments. For insurers, managing agents and brokers around Lloyd's we replace spreadsheet workflows with internal tools: bordereaux intake, referral queues and approvals, connected to the policy systems you already run.
How does your rate compare to hiring in London?+
ITJobsWatch puts the median advertised salary for a software engineer in London at roughly £99,000. Our published rate is $35/hour, with a $5,000 minimum engagement. There is no recruiting time and no employment overhead, and we can start within days of the first call. Most clients begin with a fixed-price two-week piece at $2,800, so you judge us on working code before committing to more.
Can you work white-label for a London agency?+
Yes. London agencies bring us in when a client project needs more senior backend, mobile or infrastructure work than the team has free. We work under your name, in your repositories and your client's tools, and you stay the face of the project. The NDA comes before specifics, the code belongs to the client from the first commit, and runbooks and architecture notes are written as we go.
Shared database, separate schemas, or a database per tenant?+
Shared tables with row-level security for most products, because it is the cheapest to run and the simplest to migrate. Separate schemas or databases when a customer contractually needs isolation, data kept in a particular region, or its own backup schedule. We design so a large tenant can move to its own database later without rewriting the application, because that request usually arrives with the biggest contract.
When should we add SSO and SCIM?+
Before the deal that needs them, not in the first month. Design the user and organisation model so SSO slots in without a data migration, then switch it on when a paying customer asks. A provider such as WorkOS saves you building SAML and SCIM yourself, which rarely pays off until enterprise customers are a large share of your revenue.
Stripe, or a merchant of record like Paddle?+
Stripe gives you the most control over plans, invoices and the checkout. A merchant of record such as Paddle takes a larger fee and becomes the seller, handling tax wherever you sell. For a small team selling internationally from the start, the merchant of record is often the simpler path. We lay out both at your price point before you choose.
Can you make the product ready for enterprise buyers?+
Yes. Enterprise buyers ask for the same things every time: single sign-on, directory provisioning, roles they can define, an audit log they can export, and admin screens their IT team can use. We design those into the data model early, so saying yes to the next large customer is a configuration change rather than a quarter of rework.
What have you built that carries over to SaaS?+
Multi-tenancy, per-organisation access and admin tooling run through most of what we build. FM360 is a multi-tenant platform with all three: organisations, apps and access managed per customer, usage analytics and login alerts. Subscriptions and billing logic we build inside the product, tested like any other code rather than left to a dashboard.