siznex-logo.png
St. Petersburg / St. Pete, FL · 300+ Projects

Custom Software &
App Development
That Generates Revenue.

One team of engineers and designers building your product from a single roadmap. No agency handoffs. No translation loss. You own everything.

Start your project Explore services

Custom Software

SaaS, ERP, APIs & enterprise apps on AWS, Azure, GCP

Mobile Apps

iOS, Android & cross-platform. Fixed price, first-try approval

Web Development

React, Next.js & Node. Conversion-focused, high-performance builds

SaaS Platforms

Scalable, multi-tenant products built to grow from day one

Avg. time to launch 8wks
98% success rate 300+ delivered
Projects delivered
300+
Web, mobile & enterprise software
Client rating
4.8/5
Verified across Google & Clutch
Project success rate
98%
On-time, on-budget delivery
Years in business
7+
Building software since 2017
What We Do

One Company for Your Entire Product Stack.

Most teams juggle separate vendors for design, development and delivery. Siznex does it all. Engineers and designers on the same roadmap, the same P&L, from day one.

01

Build — Custom Software Development

We engineer web application development, mobile apps, SaaS platforms and ERP systems using cloud-native architecture. Every product built to scale from day one, no rewrites, no tech debt surprises.

Web Apps Mobile Apps SaaS Platforms ERP Systems APIs
Explore services
02

Design — Web & Mobile App Development

We design and build web applications, mobile apps and custom software that convert. Every interface is grounded in user research and engineered for performance, React, Next.js, React Native and Flutter.

Web Apps iOS & Android UI / UX Design React Native Flutter
Explore services
Custom SoftwareMobile AppsWeb DevelopmentSaaS PlatformsERP SystemsAPI DevelopmentCloud Native
7+
Years in business
300+
Projects delivered
98%
Client satisfaction
50+
Active clients
25+
Team members
10+
Countries served
01 / Services

Custom software, web and mobile development, everything under one roof.

From conversion-focused marketing sites to complex web application development, auth, dashboards, API development and integrations on React, Next.js and Node.js. Performance and accessibility built in at code time, not bolted on after.

React / Next.jsNode.jsAPI DevelopmentHeadless CMSE-commerce
View service

Swift and SwiftUI for iOS, Kotlin for Android, React Native and Flutter for cross-platform. MVP to enterprise, fixed price, first-try App Store and Play Store approval guaranteed.

Swift / SwiftUIKotlinReact NativeFlutterHealthKit
View service

Bespoke software around your enterprise workflows, microservices, multi-tenant SaaS, ERP, API development and agentic AI with RAG pipelines. Node.js, AWS, Azure and GCP. You own all source code.

Node.jsAWS / Azure / GCPSaaS PlatformsERP SystemsAgentic AI
View service
02 / Process

Our Product
Engineering Process.

Four phases. Each ends with a deliverable you can see, test and approve before the next one starts.

01
Week 1–2

Discovery & Strategy

Deep audit of your business, audience, competitors and KPIs. We build the brief every phase points back to.

  • Positioning and ICP document
  • KPI tree and prioritised roadmap
  • Budget envelope by line item
  • Competitive analysis report
02
Week 3–5

Design & Architecture

Brand work, UX research, wireframes and hi-fi prototypes. Architecture document before a single line of code.

  • Clickable hi-fi prototype
  • Figma design system
  • Technical architecture doc
  • Tech stack sign-off
03
Week 6–10

Build & Launch

Engineering sprints with a demo every Friday. CI/CD, automated tests, cloud deployment and a real launch.

  • Production-ready software
  • Automated test coverage
  • Cloud infra and monitoring
  • App Store / Play Store submission
04
Ongoing

Support & Scale

Dedicated support, monitoring and iterative improvements, your product keeps evolving long after launch day.

  • Monthly performance reports
  • Maintenance and monitoring
  • Roadmap for next quarter
  • You own all code and accounts
03 / Industries

Vertical-Specific Software Expertise.

Healthcare
HIPAA · FHIR · EHR
Fintech
Payments · Insurance · Trading
Real Estate
IDX · MLS · Broker portals
E-commerce
Headless · Shopify · Marketplace
Fitness
HealthKit · Wearables · Gym SaaS
Enterprise
ERP · Legacy · Automation

Healthcare Software

HIPAA-compliant platforms with native EHR integration, telemedicine apps and patient management systems built for clinicians.

EHR Integration
Native Epic, Cerner, Athenahealth via FHIR R4 APIs. Real-time patient data sync.
HIPAA Compliance
Encryption at rest and in transit, audit logs, BAA agreements, RBAC.
HL7 & FHIR R4
Lab results, prescriptions, appointment management out of the box.
Mobile Health
HealthKit, Google Fit integration, wearable data sync, push notifications.
HIPAAFHIR R4Epic IntegrationHL7TelemedicineHealthKit

Fintech Platforms

Payment platforms, trading dashboards, insurance broker systems and lending portals on secure microservices architecture.

Payment Systems
Stripe integration, multi-currency, subscription billing, escrow flows.
Insurance Software
Broker portals, policy management, claims processing, document automation.
Trading Platforms
Real-time market data, portfolio management, order execution systems.
Security
Role-based access control, full audit trails, SOC 2 ready architecture.
StripeInsurance BrokerLendingRBACMicroservices

Real Estate Tech

Property listing platforms, CRM and lead management systems, virtual tour apps and broker portals with IDX and MLS integration.

IDX / MLS Feeds
Live property data feeds, automated sync, advanced search and filtering.
Broker CRM
Lead capture, pipeline management, automated follow-up sequences.
Virtual Tours
360° tours, interactive floor plans, video walkthroughs embedded.
Valuation Models
Automated valuation, comparable sales analysis, market trend dashboards.
IDX IntegrationMLS FeedsVirtual ToursAVM

E-Commerce Platforms

Custom storefronts, headless commerce, marketplace platforms and subscription billing, built for performance and conversion.

Headless Commerce
Custom front-end on Shopify, WooCommerce or fully bespoke stacks.
Marketplace
Multi-vendor platforms, seller dashboards, split payments, reviews.
Subscription Billing
Recurring billing, trial management, dunning, proration.
Performance
Sub-1s page loads, Core Web Vitals green, conversion rate optimised.
ShopifyHeadlessMarketplaceSubscription

Fitness Apps

Workout tracking apps, gym management platforms, nutrition logging and wearable integrations, HealthKit and Google Fit native.

Workout Tracking
Custom exercise libraries, progress charting, personal records, streaks.
Wearable Sync
Apple Watch, Garmin, Fitbit, heart rate, GPS, sleep data.
Gym Management
Membership, class booking, trainer scheduling, billing portal.
Nutrition
Food database, macro tracking, meal planning, barcode scanner.
HealthKitGoogle FitApple WatchGym SaaS

Enterprise Software

ERP systems, internal tooling, workflow automation and legacy modernization. Monoliths migrated to cloud-native microservices without downtime.

ERP Systems
Custom ERP replacing legacy tools, procurement, HR, finance, ops.
Legacy Modernization
Strangler fig pattern, zero-downtime migration, full test coverage.
Workflow Automation
RPA, agentic AI, document processing, approval chains, notifications.
Cloud Migration
AWS, Azure, GCP, infra as code, CI/CD, monitoring and alerting.
ERPCloud MigrationRPAAgentic AI
Healthcare Mobile App Development
HIPAA-Compliant Apps.
For Clinicians.
Loved by Patients.

We build HL7 FHIR-compliant healthcare platforms with real-time patient data sync, lab results, prescriptions and appointment management out of the box.

Native integration with Epic, Cerner and Athenahealth via FHIR R4 APIs
HIPAA-compliant architecture, encryption at rest and in transit, BAA agreements
HealthKit and Google Fit native, wearable data, Apple Watch support
Real-time patient data sync, lab results, prescriptions and appointments
See healthcare app development
EHR & API Integration
Native integration with Epic, Cerner, Athenahealth and custom EHR systems via FHIR R4 APIs. Real-time patient data sync, lab results, prescriptions and appointment management out of the box.
HIPAA Security Architecture
Encryption at rest and in transit, role-based access control, comprehensive audit logging, Business Associate Agreements and HIPAA-ready cloud infrastructure on AWS GovCloud.
HL7 & FHIR R4 Compliance
Full HL7 FHIR R4 implementation, patient resources, observation resources, medication requests, appointment resources and care plan objects all natively supported.
Mobile Health (mHealth)
HealthKit, CareKit and ResearchKit integration. Apple Watch, Garmin and Fitbit data sync. Push notification system for medication reminders and appointment alerts.
05 / Testimonials

Customer reviews.

4.8
4.8/5 based on 300+ projects

Siznex migrated our entire insurance broker platform from a legacy monolith to cloud-native microservices on AWS. Zero downtime, full test coverage, same team two years on.

JL
Jamie L.
CTO, InsureTech Co.
Google

We needed an agentic AI system to process unstructured contracts and push structured data into our ERP. Siznex delivered it in six weeks, in production, zero bugs.

SR
Sarah R.
VP Operations, Enterprise Corp
Clutch

Multi-tenant SaaS platform, Stripe billing, role management, full analytics dashboard. Shipped in eight weeks. We are still on the same team two years later.

AT
Alex T.
CEO, SaaS Startup
Google
06 / FAQ

Quick answers.

Questions prospects ask on the first call. If yours is not here, there is a real person reading every message.

Direct line(727) 264 0270 Emailinfo@Siznex.com

We build custom software, web apps, mobile apps, SaaS platforms and ERP systems. From the first brief to launch and beyond, one team owns the entire build, no agency handoffs, no translation loss.

An MVP web or mobile app typically ships in 8–12 weeks. A full enterprise platform or SaaS build runs 12–24 weeks depending on scope. We publish a timeline in week one, every phase has a defined deliverable and a Friday demo.

Fixed price on all software engagements. You get a scoped proposal before a single line of code is written, budget envelope, timeline and deliverables locked in. No surprise invoices mid-project.

You own everything. Full source code and all brand assets. No vendor lock-in, no hostage code, no proprietary frameworks you cannot maintain independently.

Yes. We build full HL7 FHIR R4-compliant platforms with native EHR integration, Epic, Cerner, Athenahealth and custom EHR systems via FHIR R4 APIs. Real-time patient data sync, lab results, prescriptions and appointment management out of the box. HIPAA-compliant architecture on every healthcare engagement.

Both. With a 98% project success rate, we have shipped MVPs for first-time founders and rebuilt core systems for companies doing $50M+ in revenue. The discovery phase is the same either way, we scope to your budget, not the other way around.

Fill out the form below or call us directly. We schedule a 30-minute discovery call, no pitch deck, no pressure. We ask about your project, timeline and budget, then send a scoped proposal within 48 hours.

Consultation, no pitch deck

Ready to build
something real?

Tell us what you are working on. We respond within one business day with a scoped proposal, no vague estimates, no padded timelines.

98% project success rate  ·  Reply within 1 business day  ·  You own all deliverables