--- title: "Custom Web Application & SaaS MVP Development Services | FixrWeb" description: "Full-stack web application development and SaaS MVPs delivered in 4 weeks. Modular architectures built with Astro 5, React, Bun, and PostgreSQL." canonical_url: "https://fixrweb.com/services/custom-apps" ai_markdown_url: "https://fixrweb.com/services/custom-apps.md" --- # Custom Web Application & SaaS MVP Development Services > FixrWeb builds full-stack web applications, B2B customer portals, and production-ready SaaS MVPs on a fixed-milestone schedule with complete source code ownership. **TL;DR / Executive Business Summary:** - **The Challenge:** Founders and enterprise teams lose momentum when agencies deliver bloated, buggy software on open-ended hourly contracts that exceed initial estimates. - **The Fix:** FixrWeb delivers modular, high-velocity web applications using Astro 5 SSR, React Islands, Bun, and PostgreSQL under fixed-price milestone agreements with weekly demos. - **Business Results:** **4-week SaaS MVP launch**, **sub-second page interactions**, **100% intellectual property ownership**, and predictable budgets. - **SaaS MVP**: A minimum viable software product engineered with core user workflows, authentication, database persistence, and billing integration ready for paying customers. - **Client Portal**: A secure web application where business clients access project milestones, upload confidential files, and manage team seats. - **Astro 5 SSR & React Islands**: Web architecture combining fast static and server-rendered HTML with isolated interactive React components loaded only when needed. - **TypeScript Full-Stack Architecture**: End-to-end type safety connecting database schemas to frontend UI components to prevent runtime errors. --- ## Core Offerings ### 1. SaaS MVP Development in 4 Weeks - Full user authentication with email verification, password reset, and OAuth2 social logins. - Stripe subscription integration with Customer Portal for automated upgrades, downgrades, and invoices. - Database architecture in PostgreSQL with Prisma or Drizzle ORM. - Transactional email templates powered by SendGrid or Postmark. ### 2. B2B Client & Customer Portals - Multi-tenant data segregation ensuring enterprise clients only access their records. - Secure direct-to-cloud file uploads (AWS S3, Cloudflare R2) with presigned URLs. - Activity audit logging and team member permission management. ### 3. Full-Stack Web Application Engineering - High-concurrency backend services powered by Bun or Node.js. - Redis caching for frequent database queries and session management. - RESTful and GraphQL API endpoints with comprehensive Swagger/OpenAPI documentation. ### 4. Application Modernization & Refactoring - Untangling monolithic legacy systems into clean, modular microservices. - Zero-downtime database schema migrations with automated rollbacks. - End-to-end automated test suites using Playwright and Vitest. --- ## Technology Stack | Layer | Technologies Selected | Core Advantage | | :--- | :--- | :--- | | **Frontend Framework** | Astro 5 SSR + React Islands | Sub-second page loads with zero unnecessary JavaScript | | **Backend Runtime** | Bun & Node.js | Low memory footprint and rapid execution speed | | **Primary Language** | TypeScript | End-to-end strict type checking | | **Database** | PostgreSQL | Proven ACID compliance and relational integrity | | **Cache Layer** | Redis | In-memory query caching and rate limiting | | **Payments** | Stripe API & Webhooks | Automated subscription lifecycle management | --- ### Q: How fast can you build and launch a functional SaaS MVP? A: We typically deliver a production-ready SaaS MVP in 4 weeks under a fixed-scope milestone agreement. This includes user authentication, database architecture, billing integration with Stripe, core product workflows, and automated transactional emails. ### Q: What technology stack do you use for custom web applications? A: We primarily build with Astro 5 Server-Side Rendering (SSR) or React, TypeScript, Bun or Node.js backend services, PostgreSQL for relational data, Redis for caching, and Tailwind CSS for responsive styling. We choose tools that maximize page speed and long-term maintainability. ### Q: Do you offer fixed-price contracts or hourly billing? A: We work predominantly on fixed-price milestones with clearly defined acceptance criteria. You know exact timelines, deliverables, and total costs upfront without billing surprises. ### Q: What happens after the application is deployed? A: We provide 30 days of post-launch warranty support to resolve any edge-case issues. We also offer ongoing maintenance retainers and dedicated managed cloud hosting. ### Q: How do you handle data security, authentication, and compliance? A: We enforce strict security practices including encrypted environment secrets, parameterized SQL queries to prevent injection, bcrypt/Argon2 password hashing or OAuth2 providers, and edge Web Application Firewall (WAF) protection. - Services Catalog: https://fixrweb.com/services/index.md - Internal Tool Building: https://fixrweb.com/services/internal-tools.md - Custom Website Building: https://fixrweb.com/services/custom-websites.md - Managed Cloud Hosting: https://fixrweb.com/services/managed-hosting.md - AI Master Index: https://fixrweb.com/llms.txt