SaaS Development Explained
What actually goes into building a software product other businesses pay to use - multi-tenancy, billing, roles, onboarding - and why the first version should be much smaller than you think.
SaaS development means building software that multiple separate customers use through a browser, paying on an ongoing basis. The distinction from other software is not technical sophistication - it is that you are running the software on behalf of everyone who uses it.
That shift creates a set of requirements that surprise people building their first product, because they sit around the feature rather than in it.
The idea is a small part of the product
Most founders arrive with a clear picture of the core feature - the thing the product does that nothing else does. That feature is usually a minority of the work.
What surrounds it:
Multi-tenancy. Multiple customers sharing one system, with absolute certainty that no customer can see another’s data. This is an architectural decision made early and expensive to change later.
Authentication and accounts. Sign-up, login, password reset, sessions, and usually multi-factor. Plus the organisational layer: a customer is a company with several users, not one person.
Roles and permissions. An admin can do things a regular user cannot. Enforced server-side, always - hiding a button is a UI decision, not a security control.
Billing. Plans, upgrades, downgrades, trials, failed payments, proration, invoices, tax. Payment providers handle the transaction; the logic around it is yours. This is consistently underestimated.
Onboarding. What happens in the first five minutes decides whether a trial converts. An empty product with no guidance loses people who would have paid.
Admin tooling. Your own view into the system: which customers exist, what state their account is in, how to fix things when support asks. Without it, every support request becomes a developer request.
Email. Verification, password reset, receipts, notifications. Plus the deliverability work to make sure they arrive.
Monitoring. You need to know when it breaks before customers tell you.
None of this differentiates your product. All of it is required. It is why a SaaS build costs more than the feature list suggests.
Multi-tenancy, briefly
Two broad approaches, and the choice has long consequences.
Shared database with tenant isolation. All customers in one database, every record tagged with a tenant identifier, every query filtered by it. Efficient and simple to operate. The risk is a missing filter leaking data across tenants - which is why isolation belongs in a data access layer, not in individual queries.
Separate database per tenant. Stronger isolation, easier per-customer backup and restore, sometimes required by enterprise buyers. More operational overhead, and migrations get harder as tenant count grows.
Most products start with the first and it is usually right. Move to the second when a customer’s compliance requirements demand it.
Scope the first version harder than feels comfortable
The most common failure in SaaS development is not technical. It is building too much before anyone uses it.
The instinct is to launch complete, because an incomplete product feels embarrassing. The problem is that you are guessing which features matter, and you will guess wrong about some of them. Every feature built before you have users is a bet placed without information.
A more useful first release:
- Solves one workflow end to end, properly
- Has real authentication and billing - you need people to actually pay
- Has enough admin tooling that you can support it
- Deliberately omits everything else
Ship that, watch how people use it, then build the next thing based on what you observed rather than what you assumed.
The discipline is in what you leave out. Almost every experienced product team will tell you their first version was still too big.
Technical decisions worth getting right early
Some things are cheap to change later. Some are not.
Hard to change: the data model, tenant isolation strategy, how authentication and permissions work, whether the architecture allows adding fields and roles without restructuring.
Easier to change: the UI, individual features, which payment provider, hosting.
Spend your early thinking on the first list. Specifically the data model - almost every serious problem in a maturing product traces back to a data model that did not anticipate how the business actually works. Understand the exceptions before you design the schema.
Costs that continue after launch
SaaS is an ongoing commitment, not a project with an end date.
Hosting and infrastructure, which scales with usage. Third-party services - payments, email, error tracking, analytics - each with its own bill. Maintenance: dependency updates, security patches, browser changes. Budget meaningfully for this every year. Support, which is a real operational cost. Continued development, because a product that stops improving starts losing customers.
Pricing has to cover all of it, not just the build.
The marketing site is a separate product
Your application and the site that sells it have different jobs, different audiences and different technical requirements.
The marketing site needs to be fast, findable and persuasive - it is a search and conversion problem. The application needs to be reliable and usable, and mostly should not be indexed at all.
Building them as one thing usually compromises both. We generally build the marketing site as a static, search-optimised site and the application separately, sharing a design language but not a codebase.
Before you start
- Confirm someone will pay. Not “would you use this” - will you pay, how much, for what exactly.
- Define the one workflow the first version must do well.
- Understand the data model, including exceptions.
- Decide the tenancy approach.
- Plan billing early. It is more work than it looks.
- Budget for year two, not just the build.
Products fail far more often from building the wrong thing than from building it badly.
We build SaaS products with a deliberately narrow first release and an architecture that makes the second and third versions cheap. Tell us what you are building, or read more about app development.