Developing a SaaS platform means building a multi-tenant web application with recurring subscriptions, self-service onboarding and infrastructure that scales with your customers. A realistic SaaS MVP costs between 8,000 and 25,000 EUR and ships in 2–4 months, a mature version starts at 30,000 EUR, and monthly operations cost roughly 100–500 EUR at the start.
We are a team of developers building custom SaaS platforms — from the first data model to recurring billing and the deployment pipeline. In this guide we lay out the architecture decisions explained in entrepreneur-friendly terms, honest phased costs and the mistakes we see most often in projects that come to us "for repairs". If you want a hands-on discussion about your idea, see our SaaS platform development page.
What sets a SaaS apart from a regular web application
A SaaS is a web application you sell as a service, simultaneously, to many customers who do not know each other — and that fundamentally changes the architecture. An internal application has a single "owner" of the data; a SaaS has hundreds or thousands, each expecting their data to be completely isolated from everyone else's.
Four things turn a regular web application into a SaaS platform:
- Multi-tenancy. Each customer (tenant) — usually a company with multiple users — sees only their own data. Isolation must be guaranteed at the architecture level, not just by a filter someone remembered to add to a query.
- Subscriptions and recurring payments. You do not sell a license once; you collect monthly or yearly. That means pricing plans, trial periods, mid-cycle upgrades/downgrades, retries on failed payments and automatically issued invoices.
- Self-service onboarding. A new customer must sign up, configure their account and reach value without calling anyone. Every manual step in onboarding is a hidden cost that grows linearly with your customer count.
- Scaling. The application must work just as well with 10 customers as with 1,000. That does not mean exotic infrastructure from day one, but decisions that do not block growth: correct indexes, queries that do not degrade linearly with volume, asynchronous jobs for heavy operations.
The practical difference: a web application "works". A SaaS must work for everyone, all the time, without your intervention. That is why the development effort is not in the visible screens but in the invisible foundation — and why estimates made "by page count" are always wrong.
Architecture decisions, in entrepreneur-friendly terms
The two architecture decisions that truly matter at the start are the multi-tenancy model and the application structure (monolith vs microservices) — everything else can be changed along the way at reasonable cost; these two cannot.
Multi-tenancy: row-level, schema-level or database-level isolation
There are three ways to isolate customer data, each with its trade-offs:
- Row-level isolation. All customers live in the same tables, every record carries a tenant identifier, and the database (PostgreSQL with Row-Level Security) refuses cross-tenant access. Cheapest to operate, simplest for migrations, scales excellently to thousands of tenants. It is our default choice for almost any B2B SaaS.
- Schema-level isolation. Each tenant gets their own schema in the same database. More visible isolation, but migrations run N times, granular backups get complicated, and at hundreds of tenants the tooling starts to suffer. It makes sense when customers explicitly require demonstrable separation.
- Database-level isolation. Each tenant has their own database. Maximum isolation — and maximum operating costs. Justified only for enterprise customers with strict contractual requirements or per-customer data residency requirements.
The trade-off in short: the more "physical" the isolation, the more you pay on every migration, backup and deployment. Our recommendation: start with row-level isolation enforced by the database, not just by application code, and keep the option of later moving large customers onto dedicated databases.
Modular monolith vs microservices: why the monolith wins at the start
Microservices solve an organizational problem — dozens of teams that want to ship independently — not a technical one. At the start you have a single team and zero traffic; microservices bring you only their costs: multiple deployments, network communication, distributed debugging, triple the infrastructure.
A modular monolith — a single application with clearly delimited internal modules (billing, authentication, the business domain) communicating through explicit interfaces — gives you the monolith's speed and the discipline that allows extracting a module into a separate service when the data demands it, not when fashion does. In our experience, the vast majority of SaaS platforms never reach the scale that justifies microservices, and those that do have, by then, both the money and the team for the transition.
Our typical stack: Next.js, PostgreSQL, European hosting
We typically build on Next.js (React) with TypeScript and PostgreSQL, hosted on European infrastructure. The reasons are pragmatic, not a matter of taste:
- Next.js covers both the marketing site (fast, indexable) and the application itself, in a single project, with one language across frontend and backend — a smaller team, faster delivery.
- PostgreSQL is the relational database with the best robustness-to-cost ratio in the industry: Row-Level Security for multi-tenancy, JSONB for flexible data, mature extensions for search and jobs.
- European hosting simplifies GDPR compliance (data never leaves the EU) and reduces latency for users in Romania and the region. Costs are comparable to or lower than the American hyperscalers.
The mandatory components of a SaaS platform
Regardless of the domain, any serious SaaS needs the same six foundation components — and they typically consume 40–60% of an MVP budget before you write the first line of your differentiating functionality.
- Authentication and organizations. User accounts, organizations (tenants), email invitations, password reset, possibly SSO for enterprise customers. The user–organization model must be designed correctly from day one: can a user belong to multiple organizations?
- Recurring billing. Stripe remains the standard for subscriptions: plans, trial periods, proration, automatic retries. Beware, however: Stripe does not issue invoices compliant with Romanian legislation. You need an additional layer that generates valid fiscal invoices and reports them to e-Factura — mandatory for B2B in Romania. This "minor" detail surprises almost everyone at budgeting time.
- Roles and permissions. Owner, admin, member — at minimum. The permission system must be enforced on the server, on every request, not just hidden in the interface.
- Admin panel. You, as the platform operator, need to see tenants, suspend accounts, grant trial extensions, investigate issues. Without an admin panel, every support request becomes a manual intervention in the database.
- Audit log. Who did what and when. Indispensable for support, security and for B2B customers who ask for it during procurement.
- GDPR. Data export on request, deletion on request, consent records, DPAs with subprocessors. For a SaaS selling to European companies, GDPR compliance is a purchasing criterion, not a formality.
The good news: these components are the same in every project, so a team that has built them several times delivers them predictably. We treat them as a standard foundation on top of which we build the logic specific to your business — if you want to see what that looks like concretely, write to us and we will show you on a demo project.
Honest costs, by phase
A professional SaaS MVP costs 8,000–25,000 EUR and takes 2–4 months; a mature version, ready for commercial scaling, starts at 30,000 EUR. On top of that come monthly operating costs of 100–500 EUR at the start. The figures below reflect the Romanian agency market in 2026, for teams delivering production code, not prototypes.
| Phase | What it includes | Indicative budget | Duration |
|---|---|---|---|
| Validation / prototype | Specifications, UX design, clickable prototype, architecture | 2,000–5,000 EUR | 2–4 weeks |
| SaaS MVP | Complete foundation (auth, organizations, billing, admin) + core functionality, launchable to real customers | 8,000–25,000 EUR | 2–4 months |
| Mature version | Integrations, reporting, public API, SSO, scaling optimizations, full e-Factura | 30,000+ EUR | 4–9 months cumulative |
| Monthly operations | Hosting, database, transactional email, monitoring, backups | 100–500 EUR/month | recurring |
| Maintenance and evolution | Security updates, new features, support | 500–2,500 EUR/month | recurring |
Where does the gap between 8,000 and 25,000 EUR for an MVP come from? From domain complexity: a scheduling SaaS has a simple data model; a billing or logistics one has dense business rules, integrations with external systems and compliance requirements. The number of roles, the integrations (accounting, ANAF, payments) and the volume of data migrated from a legacy system are the main multipliers. We detailed the mechanics of estimation in our custom software development guide, and if you are interested strictly in the first launchable version, we wrote separately about building an MVP — cost, duration and what to cut without regrets.
Monthly operating costs at the start are modest: application and database hosting (40–150 EUR), transactional email (0–50 EUR), monitoring and error tracking (0–100 EUR), backups and domains. They grow with traffic — which is exactly when you also have the revenue to cover them.
The classic mistakes that make a SaaS project expensive
The most expensive mistakes in a SaaS are not bugs but architecture decisions postponed or made out of inertia — they are paid for with months of rewriting at exactly the moment the product starts gaining traction.
- Premature microservices. The team starts with 5–6 separate services "to be scalable". The result: three months lost on infrastructure, distributed debugging for every bug and a demo that still does not exist. The modular monolith delivers the same functionality in half the time.
- Multi-tenancy improvised late. The application is built for a single customer, then "we adapt it for many". Adding the tenant identifier retroactively, in every table and every query, with real isolation guarantees, is one of the riskiest operations in software — and a cross-tenant data leak can bury a B2B SaaS reputationally. Multi-tenancy is decided on day one.
- No data migration plan. Your customers do not start from zero — they have data in Excel, in the old system, at a competitor. Without import and assisted migration, every new customer means days of manual work, and self-service onboarding remains an illusion. The migration plan is designed together with the data model, not after launch.
- Underestimating Romania-compliant invoicing. "We add Stripe and we are done" works until the first invoice requested by a Romanian B2B customer. Fiscal invoices with series and number, correct VAT rates, e-Factura reporting, credit notes — all of these are functionality to build and test, not a checkbox. Budget them from the start.
- Foundation without a product. The flip side: six months spent on the "perfect" platform with no functionality a customer would pay for. The standard foundation must be delivered quickly and predictably, so that time and budget remain for what differentiates you.
In-house team or agency?
For the initial build of a SaaS, a specialized agency is almost always faster and cheaper than hiring your own team; an internal team becomes cost-effective after the product has revenue and a steady development cadence.
The math is simple: a SaaS MVP simultaneously requires architecture, frontend, backend, DevOps and design skills — meaning at least 2–3 senior people. Hired in Romania, that means 10,000–18,000 EUR/month in salary costs, plus 2–3 months of recruiting, before the first line of code. An agency that has already built the SaaS foundation many times delivers the complete MVP for the budget of two or three months of that payroll.
The combination that works best in practice: the agency builds version 1 and operates the product in the first months, then the handover happens gradually to the internal team you hire from revenue, not from capital. For that handover to be possible, what you receive at the end matters enormously. We always hand over:
- The complete source code, in your repository, with full rights — no dependency on us and no hidden licenses;
- Documentation: architecture, data model, technical decisions and local setup instructions, so any competent developer can take over the project;
- Working CI/CD: an automated test and deployment pipeline, so shipping to production is a button, not a ritual;
- Infrastructure on your accounts: hosting, domains, external services — all in your company's name, from the start.
The right test for any vendor: "If the collaboration stops tomorrow, can I continue development with someone else without rewriting anything?" If the answer is not an unhesitating "yes", the structure of the collaboration is wrong.
Conclusion: a good SaaS is decided at the architecture stage
A successful SaaS platform is 20% idea and 80% disciplined execution: multi-tenancy decided on day one, a modular monolith instead of premature microservices, a standard foundation delivered predictably and invoicing that matches Romanian fiscal reality. With a budget of 8,000–25,000 EUR and 2–4 months, a solid MVP is realistic; with the wrong decisions, the same money buys a prototype that has to be rewritten.
If you are preparing a SaaS platform — whether you only have the idea or already have a creaking prototype — read our SaaS platform development page and then let's talk concretely: send us a few lines about your project through the contact page and we will come back with an honest assessment of architecture, budget and timeline — no obligations and no corporate jargon.
Frequently asked questions
How much does SaaS platform development cost in Romania?
A professional SaaS MVP costs between 8,000 and 25,000 EUR, depending on domain complexity, integrations and roles. A mature version, ready for commercial scaling, starts at 30,000 EUR. On top of that comes monthly operation: roughly 100–500 EUR/month at the start.
How long does building a SaaS MVP take?
Realistically, 2–4 months from specifications to launch to the first paying customers, if scope is kept under control. Projects that take longer usually suffer from unbounded scope, not technical complexity.
Which multi-tenancy model should I choose?
For the vast majority of B2B SaaS products, row-level isolation (with Row-Level Security in PostgreSQL) is the right choice: cheapest to operate and scalable to thousands of tenants. Schema-level or separate-database isolation is justified only for enterprise customers with strict contractual requirements.
Can I use only Stripe for invoicing in Romania?
Not entirely. Stripe handles subscriptions and payments excellently, but it does not issue fiscal invoices compliant with Romanian legislation and does not report to e-Factura. You need an additional compliant invoicing layer — a budget item we include as standard in our projects.
Do I receive the source code at the end of the project?
With us, yes — in full. Source code in your repository, architecture documentation, working CI/CD and infrastructure on your company's accounts. We recommend demanding the same terms from any vendor, whoever you work with.