Custom Software Development

Complete guide to custom software for companies. From planning to implementation and maintenance.

Custom software development means building applications designed around your company’s specific processes, instead of forcing your business to fit a generic product. At ASD Solutions we do it with an in-house senior team in Spain, no outsourcing, a fixed price agreed before starting and no vendor lock-in. The entry point is a 190 € technical audit with an initial diagnosis in 72 hours.

Senior Engineers, 6+ Years
Fixed Price
Full Guarantee
€190
Technical audit
€1,500+
Projects from
6+
Years of experience
100%
Code ownership

How we work

  1. 01
    Kick-off
  2. 02
    Proposal
  3. 03
    Development
  4. 04
    Delivery
  5. 05
    Support

Quick guide to custom software

The essentials first. Open each block only if you want the detail.

What is custom software development?

Custom software is built around how your team actually works. Your business processes drive the design, not the other way around like Salesforce, SAP or generic SaaS.

  • No more workarounds: every screen and workflow fits your real process, not standard limits.
  • What companies are buying: custom web applications, mobile apps and integrated backend systems.
  • The payoff: automated processes, fewer errors, more productive teams.
  • Any size: from a control panel or client portal to a full ERP or multi-tenant SaaS.

In Spain this market has grown 18% a year since 2022, as SMEs digitalise faster and ditch Excel, Access or underused ERPs for tools that actually fit.

Getting the scope right matters most: what problem it solves, who uses it, what it integrates with, and how it grows over the next 3-5 years.

When do you need custom software?

You don't always need custom software. But a few clear signs tell you that off-the-shelf tools have hit their limit and it's time to build your own.

  • Spreadsheets run critical work and people lose track of versions when several edit at once.
  • Your CRM or ERP falls short, so your team patches the gaps with manual workarounds.
  • Systems don't talk to each other, or rivals simply work faster with their own digital tools.
  • Want to dig deeper? Read custom vs commercial software and how to migrate from Excel to a professional solution.

Data volume is the giveaway. Once you manage thousands of daily records in shared spreadsheets, you've outgrown generic tools. A well-designed relational database stops data loss, keeps information consistent and gives you reports Excel can't.

How much does custom software development cost in Spain?

Pricing tracks scope, plain and simple. A basic web app starts around €600, while a full enterprise platform can run past €6,000.

  • What moves the budget: number of screens and user roles, integrations (ERP, CRM, payments), GDPR or PCI-DSS rules, and UI polish.
  • Fixed price by phase: start with a tight scope, then expand based on real results.
  • Want the full breakdown? See our guide to software development costs in 2026 with ranges by project type.

A phased build keeps risk low. Phase 1 is an MVP with core features (€600-3,000), Phase 2 adds integrations and automation (€1,000-5,000), and Phase 3 covers optimisation, analytics and advanced features (€3,000-6,000).

You validate the product with real users from day one and decide where to invest based on data, not guesses.

Development process: from idea to production software

We build your custom software in 5 clear phases, and the code is yours from day one, documented and versioned in Git.

  • Discovery (1 week): we map your processes, requirements, integrations and a technical roadmap.
  • Design (1 week): architecture, data model, user flows and wireframes.
  • Development (2-6 weeks): 2-week sprints, each ending in a demo to validate progress.
  • Testing and QA (1-2 weeks): unit, integration, E2E and security tests.
  • Deployment and support: we go live, train your team and keep helping.

We work in Scrum with React and TypeScript on the frontend, Node.js and Golang on the backend, PostgreSQL and MongoDB for data, and AWS or Google Cloud for infrastructure.

You see everything as it happens: the repo, the task board and staging environments. At the end you get full documentation, training and a warranty period.

Types of custom software we develop

Web apps, mobile apps, integrations, legacy migrations and SaaS platforms are our daily bread. Most projects mix a few of these.

  • Web apps: corporate portals, internal panels, dashboards and project management. See custom web development vs CMS like WordPress.
  • Mobile apps: native iOS (Swift) and Android (Kotlin), or cross-platform with Flutter and React Native.
  • Integrations and APIs: we link your ERP, CRM, billing and logistics via REST, GraphQL and webhooks. See our ERP and CRM integration guide.
  • Legacy modernisation: we move old Visual Basic, Access or Delphi apps to modern tech, keeping your data. See legacy application modernisation strategies.

SaaS platforms: selling a digital tool to other companies? We build multi-tenant SaaS with subscription management, automated billing, per-client admin panels and horizontal scaling.

Maintenance and software evolution

Launch day is the start, not the finish. Live software needs ongoing care to stay secure and fast as your business grows.

  • SLA plans with proactive monitoring, guaranteed response times and monthly development hours.
  • Ongoing upkeep: security patches, bug fixes, performance tuning and new browser/OS support.
  • Read why preventive maintenance pays off across the software lifecycle.

Skipping maintenance always costs more. An unupdated system piles up security holes, frustrating bugs and slow performance. Prevention runs 15-20% of the initial project cost per year, far less than fixing a critical failure.

Security and regulatory compliance

GDPR compliance and security aren't extras we bolt on at the end. We design them into every app from the first commit.

  • Security by design: OAuth 2.0, JWT and SSO authentication, plus encryption in transit and at rest.
  • Threat protection: OWASP Top 10 coverage, code audits and automated security testing.
  • Safe deploys: CI/CD pipelines scan code and dependencies, with instant rollback. Read our guide on DevOps for Spanish companies.

Why choose ASD Solutions as your development agency?

We're a Spanish custom-software team of engineers and consultants, not a code factory. We build software that serves your business goals, with over 50 projects delivered.

  • Total transparency: fixed budgets, demos every 2 weeks, your repo from day 1.
  • Your code, yours: documented, with no proprietary lock-in.
  • Senior team: engineers with 6+ years average experience, plus SLA-backed support.
  • Local presence: teams in Madrid, Barcelona and Valencia who know each region.
  • Need technology consulting, to build your web application or create your mobile app?

Talk to our team for a free discovery session and we'll map out the right approach for you.

Company, agency or freelance: which to pick for your project

CriterionCompanyAgencyFreelance
Stable team Yes, payroll with multiple roles Variable, may rotate One person
Long-term continuity Formal retainers and maintenance Per project High risk if they leave
Legal accountability Registered company (SL) Company or freelance Self-employed
Typical mid-project rate €1,500 – €5,000+ Similar or higher €500 – €3,000
Up-front technical audit Yes, €190 credited if hired Optional Rare
Multi-stack coverage Backend, frontend, cloud, mobile, AI Usually specialised 1–2 stacks
Senior engineer on every project Yes, no subcontracts or juniors Variable The freelancer

ASD Solutions is a registered company (SL) with a dedicated senior engineer on every project. Transparent pricing starting at €190.

FAQ: Software development companies in Spain

How much does it cost to hire a software development company in Spain?

At ASD Solutions pricing is public: €190 technical audit (credited if you hire us), from €300 for a quick fix, from €1,500 for a mid-sized 4–8 week project, from €5,000 for enterprise platforms and from €500/month technical retainer. We deliver a fixed quote after the free kick-off call.

What is the difference between a company, an agency and a freelance developer?

A company (SL) offers a formal contract, continuity and a stable team. An agency is similar but the team may rotate. A freelancer is a single self-employed developer, great for small projects but with higher continuity risk. For mid/long-term work or ongoing maintenance, a company reduces both operational and legal risk.

Who actually delivers the work at ASD Solutions?

A senior engineer with 6+ years of experience in backend, distributed systems and cloud. We do not subcontract to juniors or third parties. You always know exactly who answers and who ships.

What tech stack do you use?

Go, React, Node.js, TypeScript, PostgreSQL, Redis, Docker, Kubernetes, AWS/GCP/Azure. We pick per case, not per fashion. If you already have a production stack, we keep it instead of imposing ours.

How long does a custom software project take?

It depends on scope: a technical audit, 3–5 business days. An MVP, 8–12 weeks. A full enterprise platform, 3–6 months. We deliver in biweekly sprints with a live demo at the end of each one.

Do you work under NDA?

Yes, we sign NDAs at no extra cost, even before the first technical call if the project requires it. It's not mandatory: if you prefer to move forward without an NDA we can too.

Where do you work from? Only Madrid?

HQ in Madrid (Paseo de la Castellana 194). 100% remote service across Spain, with on-site visits on demand in the main cities (Madrid, Barcelona, Valencia, Seville, Bilbao, Málaga, Zaragoza, Vigo…).

What happens after you deliver the project?

We offer technical retainers from €500/month covering proactive review, bug fixes, incremental improvements and incident availability. No mandatory long-term contract: it renews month by month.

Ready for your custom software project?

Free Consultation