// US-based FastAPI developers · SaaS
Free project plan & cost estimate in 48 hours.
Senior FastAPI developers for SaaS companies, based in the US
Engineers who have shipped multi-tenant products, care about uptime and onboarding, and help your roadmap move faster without piling up debt.
- Interview engineers before you pay anything
- 100% U.S.-based, working your hours
- No brief or spec needed to get started
First 5 Dev Hours Free
Project plan. Roadmap. Cost & ROI estimation.
Real engineers. Real conversations.
Talk to an engineer. Not a salesperson.
Free · No commitment · Project-focused call
Most teams interview matched engineers within a week
Not the right fit? We bring in a replacement
Get your free project plan
Three quick steps. No brief needed.
Free · No commitment · Reply within one business day
// teams we've worked with
“NextGen scaled us from 2 to 7 dedicated engineers in under a quarter. Enterprise-grade capacity, zero agency drag.”
Sound familiar?
- The roadmap is slipping and hiring can't keep up.
- Tech debt makes every new feature slower to ship.
- Performance and reliability issues are showing up in churn.
- You need senior engineers who can own features end to end.
What our FastAPI engineers build for SaaS companies
SaaS product work
Multi-tenant features, billing, permissions, and dashboards built to scale.
APIs & microservices
Typed FastAPI services with auto-generated docs.
AI & data back-ends
APIs serving models, search, and data pipelines.
How it works
- 01
Pick a time
Book a 30-minute project call directly in our calendar.
- 02
Talk through the problem
Tell us what needs building, what's stuck and what success looks like. No spec needed.
- 03
Your plan in 48 hours
Get your project plan, roadmap, cost and ROI estimates. The plan is yours to keep.
- 04
First 5 dev hours free
Agree the scope with our team. Decide whether to continue before any paid work begins.
Common questions
Will this turn into a sales pitch?
No. The call is about your project: what needs building, what's stuck, and whether we have the right engineers. If we're not a fit, we'll say so.
What do I get for free?
A project plan, roadmap, cost estimate and ROI estimate within 48 hours of your project call. Your first 5 development hours are free, too. We agree the scope and any paid work with you before proceeding.
Do I need a spec or brief?
No. Tell us the problem in plain words and we'll help shape the scope with you.
Are the engineers really in the U.S.?
Yes. Every engineer lives and works in the United States. No offshore hand-offs, and that's in the contract.
What our clients say
"NextGen scaled us from 2 to 7 dedicated engineers in under a quarter. Enterprise-grade capacity, zero agency drag."
"Their R&D tax credit workflow platform paid for itself in the first filing season."
"AI-native from day one. Our IRS transcript pipeline runs 24/7 without a human in the loop."
"Property tax appeals used to take weeks. Their comp analysis tooling turned it into hours."
"The AI intake agent handles our tier-1 patient calls with a hand-off cleaner than our old call center."
"POS, inventory, ordering — all unified. We finally have one source of truth across every location."
"The procurement platform paid for itself in the first quarter of use."
"They shipped our matching engine in 6 weeks. Our old team would've taken 6 months."
"Enterprise-grade delivery without the enterprise-agency price tag."
"Their team plugged into our sprint on day one. Zero ramp time."
"NextGen scaled us from 2 to 7 dedicated engineers in under a quarter. Enterprise-grade capacity, zero agency drag."
"Their R&D tax credit workflow platform paid for itself in the first filing season."
"AI-native from day one. Our IRS transcript pipeline runs 24/7 without a human in the loop."
"Property tax appeals used to take weeks. Their comp analysis tooling turned it into hours."
"The AI intake agent handles our tier-1 patient calls with a hand-off cleaner than our old call center."
"POS, inventory, ordering — all unified. We finally have one source of truth across every location."
"The procurement platform paid for itself in the first quarter of use."
"They shipped our matching engine in 6 weeks. Our old team would've taken 6 months."
"Enterprise-grade delivery without the enterprise-agency price tag."
"Their team plugged into our sprint on day one. Zero ramp time."
Hire US-based FastAPI developers to build and maintain multi-tenant SaaS backends, subscription workflows, and customer-facing APIs. With Pydantic v2, SQLAlchemy 2.0, and PostgreSQL, the key challenges include tenant isolation, authorization, and migrations that preserve active customer workflows. Redis caching and Celery workers introduce their own questions about tenant-aware keys, duplicate jobs, and consistent behavior when a subscription changes.
NextGen Coding Company's senior engineers work your hours and participate in your standups, whether the immediate task is tracing slow Uvicorn requests or untangling subscription entitlement checks. Every engineer lives and works in the US, with no offshore subcontracting. We sign an NDA and full IP assignment before touching code, and provide a replacement with a proper hand-over if the fit isn't right.
Frequently asked questions
- How should a FastAPI SaaS application isolate tenant data?
- Choose an isolation model deliberately: shared tables with tenant identifiers, separate schemas, or separate databases. FastAPI dependencies can resolve tenant context, but every query and background job must enforce it. PostgreSQL row-level security can add protection when configured correctly. Test cross-tenant access attempts, including exports, cached responses, and administrative endpoints.
- Can FastAPI support SaaS subscriptions and feature entitlements?
- Yes. Keep billing provider events separate from the authorization decisions your product makes. Store subscription state, process webhook retries idempotently, and define what happens during failed payments or plan changes. Entitlement checks should run on the server, with tests covering cancellation, seat limits, and delayed or out-of-order billing events.
- How do you improve a slow FastAPI SaaS backend?
- Measure first with OpenTelemetry traces, query timings, and representative load tests using Locust or k6. Common problems include blocking network calls inside async routes, N+1 queries, oversized responses, and exhausted connection pools. Check tenant-specific usage patterns before adding workers or Redis caching, which can hide rather than fix expensive queries.
- Should FastAPI BackgroundTasks or Celery handle SaaS background jobs?
- BackgroundTasks suits small, noncritical actions that can run in the application process after a response. Use a durable queue such as Celery with RabbitMQ for exports, scheduled integrations, or work requiring retries. Jobs should carry tenant context, tolerate duplicate delivery, and expose status without letting one customer read another's results.
- Can we hire a FastAPI developer to work on an existing SaaS codebase?
- An existing service is a valid starting point. Share its Python and FastAPI versions, test coverage, deployment process, and highest-priority backlog items. Book a 15-minute call to define the role. Most teams interview matched engineers within a week, and senior engineers join your regular standups during your working hours.
- Are your developers really based in the US?
- Yes. Every engineer lives and works in the United States. No offshore subcontracting and no hand-offs to another team. That's written into the contract.
- How fast can someone start?
- Most teams interview matched engineers within a week of the first call. Start dates depend on your interview process.
Related reading
- How to hire a software developer
What to check before you sign.
- Hiring test for senior engineers
How to vet senior talent fast.
- Senior engineer salary guide 2026
What the market pays.
- Onshore vs offshore vs nearshore
The honest tradeoffs.
- Forward deployed engineers
Need an owner, not just capacity?
- Resource library
Every guide and benchmark we publish.
Start your project request
Tell us what you're building — engineering capacity, AI, QA, cloud, or a fixed-scope software engagement. Our NYC team responds within one business day.
- Response within 1 business day
- 30-minute discovery conversation
- Recommended engagement model & pricing
- NYC-focused — in-person available
Inbound sales only. All form information is encrypted in transit.