Services // SaaS Engineering

SaaS Products, Built to Charge.

CodeOpx builds subscription products in Next.js: authentication and roles, Stripe billing with webhooks that survive retries, multi-tenant PostgreSQL, background jobs, an admin panel, Docker deployment, and AI features where they earn their place. A first paying-customer release typically lands in four to ten weeks — in your repository, milestone by milestone.

Scope Your Build Order on Fiverr

What every build includes

The scaffolding is the same in every SaaS. Getting it right once is why the calendar goes to your actual product instead of to plumbing.

key

Auth and roles

Email and OAuth sign-in, sessions, password reset, organisations, invitations, and per-role permissions checked server-side.

credit_card

Stripe billing

Subscriptions and usage plans, trials, proration, the customer portal, and idempotent webhooks so a retry never double-charges.

database

Multi-tenant data

PostgreSQL schema with tenant isolation enforced at the database layer, migrations, and seed data for a realistic staging environment.

api

APIs and integrations

REST endpoints, webhook receivers and senders, background jobs and queues, third-party sync, and rate limiting that holds up.

smart_toy

AI where it pays

OpenAI, Claude, or Gemini features — assistants, retrieval, extraction — with caching, model tiering, and usage caps per customer.

rocket_launch

Deployment

Dockerised, CI/CD from your branch, deployed to Vercel, Cloud Run, or your own VPS, with backups and monitoring in place at launch.

Stack

Frontend: Next.js App Router, React, Tailwind CSS, server components and streaming where they cut load time.

Backend: Node.js, route handlers and server actions, background workers, Redis for queues, caching, and rate limits.

Data and payments: PostgreSQL, Stripe subscriptions and webhooks, S3-compatible storage, transactional email.

Infrastructure: Docker, GitHub Actions, Vercel, Google Cloud Run, or a VPS — with backups and monitoring from day one.

Remote-first

How remote collaboration works

Founders and product teams hire us remotely for Next.js builds, APIs, and launches—without losing velocity across time zones.

Book a call

publicFully remote—teams worldwide. English-first written updates and scheduled video calls when decisions need sync time.
scheduleOverlap for reviews and workshops is agreed in discovery (e.g. Americas / EU / UK windows) so feedback does not stall builds.
forumAsync between calls: recap notes, Loom-style walkthroughs when useful, and a single thread per milestone so context stays searchable.
hubWe meet you in your stack where possible—GitHub/GitLab, Figma, Linear, Jira, Notion—instead of forcing a foreign workflow.
paymentsMilestone billing with written scope, deliverables, and acceptance checks per phase so remote budgeting stays predictable.
verified_userNDA-friendly process; code and design assets live in repositories and workspaces you control unless we agree otherwise.

Who this is for

Founders taking a subscription product to first revenue, and teams adding billing, tenancy, or AI to something that already has users.

Typical timeline

Four to ten weeks to a paying-customer release, shipped in reviewable milestones rather than one long silence followed by a reveal.

Related services

Add AI integration, get it running on your own VPS, or start with UI/UX design.

Case study snapshots

Representative engagements that mirror how we collaborate on discovery, design, and engineering—not stock filler. Read the full narrative on each case page.

SaaS product

Nexus Platform

Multi-tenant SaaS shell with auth, billing hooks, and performance-minded UI delivery.

Read case studyarrow_forward

FinTech app

Lumina

Data-heavy dashboards with emphasis on legibility, trust, and audit-friendly layouts.

Read case studyarrow_forward

View full portfolio →

Frequently asked questions

How much does it cost to build a SaaS MVP with Next.js?: A focused MVP — authentication, billing, a working core feature, and an admin view — typically runs in the four-to-five figure range depending on how much product logic sits behind the login. You get a written milestone plan with a price per milestone before engineering starts, so scope changes are a decision rather than a surprise invoice.
How long does it take to launch a SaaS MVP?: Four to ten weeks for a first paying-customer release, shipped in milestones you can review as they land. The parts that are the same in every SaaS — auth, subscriptions, webhooks, roles, emails — are not rebuilt from scratch each time, so most of the calendar goes to what makes your product different.
Do you integrate Stripe subscriptions?: Yes: subscription and usage-based plans, Checkout or embedded elements, the customer portal, proration on upgrades and downgrades, trials, coupons, tax handling, and — the part that is usually broken elsewhere — idempotent webhook handling so a retried event never double-charges or double-provisions.
What does multi-tenancy look like in your builds?: Organisations, per-organisation roles and invitations, and data isolation enforced at the database layer rather than trusted to application code. This is decided at the start, because retrofitting tenancy into a live product is one of the most expensive rewrites there is.
Do we own the code?: Yes, entirely. Work happens in your repository from the first commit, on standard open-source tooling with no proprietary lock-in, and handover includes documentation and deployment runbooks so another developer can pick it up.
Can you add AI features to our SaaS?: Yes — chat assistants, retrieval over your own documents, extraction, and agent workflows using the OpenAI, Claude, or Gemini APIs, with cost controls and evaluation built in. See the AI integration service page for how that work is scoped.
Can you take over an existing SaaS codebase?: Yes. That starts with a paid audit: architecture, dependency and security state, test coverage, and the highest-risk areas, delivered as a written report with a prioritised plan. You are free to take that plan elsewhere.

Guides for Buyers

How Much Does Web Development Cost for Startups in 2026?

Read guide

Agency vs Freelancer for Web Development: Which Is Better?

Read guide

From idea to first paying customer.

Bring the product idea or the half-built repository. You get a milestone plan with a price per milestone before any code is written.

Request a Quote Order on Fiverr

Fiverr gig: Next.js SaaS developer — Stripe, APIs, PostgreSQL, Docker, AI integrations — buyer protection and escrow handled by Fiverr.

Loading Legacy

SaaS Products, Built to Charge.

What every build includes

The scaffolding is the same in every SaaS. Getting it right once is why the calendar goes to your actual product instead of to plumbing.

key

Auth and roles

Email and OAuth sign-in, sessions, password reset, organisations, invitations, and per-role permissions checked server-side.

credit_card

Stripe billing

Subscriptions and usage plans, trials, proration, the customer portal, and idempotent webhooks so a retry never double-charges.

database

Multi-tenant data

PostgreSQL schema with tenant isolation enforced at the database layer, migrations, and seed data for a realistic staging environment.

api

APIs and integrations

REST endpoints, webhook receivers and senders, background jobs and queues, third-party sync, and rate limiting that holds up.

smart_toy

AI where it pays

OpenAI, Claude, or Gemini features — assistants, retrieval, extraction — with caching, model tiering, and usage caps per customer.

rocket_launch

Deployment

Dockerised, CI/CD from your branch, deployed to Vercel, Cloud Run, or your own VPS, with backups and monitoring in place at launch.

Stack

Frontend: Next.js App Router, React, Tailwind CSS, server components and streaming where they cut load time.

Backend: Node.js, route handlers and server actions, background workers, Redis for queues, caching, and rate limits.

Data and payments: PostgreSQL, Stripe subscriptions and webhooks, S3-compatible storage, transactional email.

Infrastructure: Docker, GitHub Actions, Vercel, Google Cloud Run, or a VPS — with backups and monitoring from day one.

Frequently asked questions

How much does it cost to build a SaaS MVP with Next.js?

A focused MVP — authentication, billing, a working core feature, and an admin view — typically runs in the four-to-five figure range depending on how much product logic sits behind the login. You get a written milestone plan with a price per milestone before engineering starts, so scope changes are a decision rather than a surprise invoice.

How long does it take to launch a SaaS MVP?

Four to ten weeks for a first paying-customer release, shipped in milestones you can review as they land. The parts that are the same in every SaaS — auth, subscriptions, webhooks, roles, emails — are not rebuilt from scratch each time, so most of the calendar goes to what makes your product different.

Do you integrate Stripe subscriptions?

Yes: subscription and usage-based plans, Checkout or embedded elements, the customer portal, proration on upgrades and downgrades, trials, coupons, tax handling, and — the part that is usually broken elsewhere — idempotent webhook handling so a retried event never double-charges or double-provisions.

What does multi-tenancy look like in your builds?

Organisations, per-organisation roles and invitations, and data isolation enforced at the database layer rather than trusted to application code. This is decided at the start, because retrofitting tenancy into a live product is one of the most expensive rewrites there is.

Do we own the code?

Yes, entirely. Work happens in your repository from the first commit, on standard open-source tooling with no proprietary lock-in, and handover includes documentation and deployment runbooks so another developer can pick it up.

Can you add AI features to our SaaS?

Yes — chat assistants, retrieval over your own documents, extraction, and agent workflows using the OpenAI, Claude, or Gemini APIs, with cost controls and evaluation built in. See the AI integration service page for how that work is scoped.

Can you take over an existing SaaS codebase?

Yes. That starts with a paid audit: architecture, dependency and security state, test coverage, and the highest-risk areas, delivered as a written report with a prioritised plan. You are free to take that plan elsewhere.

From idea to first paying customer.

Bring the product idea or the half-built repository. You get a milestone plan with a price per milestone before any code is written.

Fiverr gig: Next.js SaaS developer — Stripe, APIs, PostgreSQL, Docker, AI integrations — buyer protection and escrow handled by Fiverr.