You will get a custom API integration for your ERP, TMS or SaaS platform
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Top Rated
Project details
Need a custom API integration that actually holds up in production? I connect ERP, TMS, and SaaS platforms to the third-party systems they depend on - with proper error handling, retries, and logging.
15+ years building integrations in .NET Core: REST, SOAP, webhooks, scheduled syncs, and message queues.
What you get:
• Integration built to your endpoints and auth requirements
• Error handling, retry logic, and rate-limit handling
• Structured logging so failures are visible, not silent
• Data mapping and transformation between systems
• Technical documentation and handover
Most integrations break in month three, not week one - when the other side changes a field, throttles you, or goes down mid-sync. I build for that from the start.
Common work: CRM and ERP syncs, payment providers, carrier and shipping APIs, accounting systems, internal service-to-service.
Send me the API docs for both sides, and I'll confirm scope and timeline before you order.
15+ years building integrations in .NET Core: REST, SOAP, webhooks, scheduled syncs, and message queues.
What you get:
• Integration built to your endpoints and auth requirements
• Error handling, retry logic, and rate-limit handling
• Structured logging so failures are visible, not silent
• Data mapping and transformation between systems
• Technical documentation and handover
Most integrations break in month three, not week one - when the other side changes a field, throttles you, or goes down mid-sync. I build for that from the start.
Common work: CRM and ERP syncs, payment providers, carrier and shipping APIs, accounting systems, internal service-to-service.
Send me the API docs for both sides, and I'll confirm scope and timeline before you order.
What's included
| Service Tiers |
Starter
$350
|
Standard
$900
|
Advanced
$2,000
|
|---|---|---|---|
| Delivery Time | 5 days | 10 days | 21 days |
Number of Revisions | 1 | 2 | 2 |
Design Customization | - | - | - |
Content Upload | - | - | - |
Responsive Design | - | - | - |
Source Code |
Optional add-ons
You can add these on the next page.
Fast Delivery
+$100 - $500
Additional Revision
+$100
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BG
Benjamin G.
May 14, 2026
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As always great to work this team, they have been invaluable over the past 6-7 years!
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Benjamin G.
Feb 3, 2026
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The team was fantastic. They consistently met deadlines, were easy to communicate with, and provided excellent flexibility and creative insight throughout the project.
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Rob H.
May 31, 2022
ASP .Net Zero (Angular and .Net Core) SPA in the Talent Analytics space: startup project
Serhii is and was an absolute pleasure to work with, he always understood the brief and made helpful recommendations throughout the project. Would definitely work with him again.
KP
Kyle P.
Jul 2, 2021
General Troubleshooting and Enchancements
Rocket Harbor has been a great team to work with over the last 4 years here at Logo Brands.
Our website was run on NopCommerce which no one in our company had much experience with. The team at Rocket Harbor was instrumental in helping us develop custom backend tools to make navigating and using the platform much easier.
If we ever needed something custom done to our website or needed an emergency fixe, Rocket Harbor was always quick to respond and did their jobs efficiently and affordably.
-Kyle Patterson: Senior Designer at Logo Brands
Our website was run on NopCommerce which no one in our company had much experience with. The team at Rocket Harbor was instrumental in helping us develop custom backend tools to make navigating and using the platform much easier.
If we ever needed something custom done to our website or needed an emergency fixe, Rocket Harbor was always quick to respond and did their jobs efficiently and affordably.
-Kyle Patterson: Senior Designer at Logo Brands
DT
Danielle T.
Sep 14, 2020
Looking for Full Stack Web developer with experience in Angular and .NET Core
I feel very confident that if you hire them they will do an amazing job
About Serhii
.NET Developer | Legacy Migration & Modernization | C#, ASP.NET Core
100%
Job Success
Lviv, Ukraine - 6:00 pm local time
Most of my work starts the same way: a system that still runs the business but has become expensive to change. Deployments are fragile, nobody wants to touch the data layer, and the original developers are gone. I assess what's actually there, tell you what's worth keeping, and migrate it in stages you can ship — not a rewrite you wait two years for.
How I approach migration
Strangler pattern over big-bang rewrites: new functionality goes into ASP.NET Core behind the existing surface while the legacy system keeps running. Domain extraction and data-layer replacement before UI work, so behavior stays verifiable. Parallel-run validation against the legacy system on every cutover.
Legacy stacks I work with: .NET Framework 3.5 through 4.8, ASP.NET WebForms, ASP.NET MVC, WinForms and WPF, VB6, classic ADO/ADO.NET, and SQL Server backends built around stored procedures.
Multi-tenant SaaS and ABP
Roughly 9,800 production hours on multi-tenant platforms built with AspNetZero and the ABP Framework — tenant isolation, module boundaries, permission systems, upgrade paths. AspNetZero is nearing end of life, and the ABP Framework is where that ecosystem is heading. If you're running AspNetZero or ASP.NET Boilerplate, migrating to ABP is work I know from the inside rather than from documentation.
ERP, TMS and platform work
Custom API and integration engineering across ERP, TMS and SaaS platforms — REST APIs in ASP.NET Core, background workers, EDI, and integrations against CRM, payment, accounting and carrier systems. Authentication with JWT, OAuth and Azure AD.
Angular and React front ends on ASP.NET Core backends: admin dashboards, operational tooling, reporting and role-based access for ERP, TMS and SaaS products.
Warehouse and inventory systems: stock movement, barcode scanning, purchase orders, cycle counts, and the mobile clients that go with them.
Azure and AWS deployment, CI/CD pipelines, monitoring, logging, and cost-aware infrastructure. Azure AI and LLM integration where it earns its place — search, summarization, classification, and Slack or Teams workflow bots.
Track record on Upwork: 11,437 hours, $400K+ billed, 100% Job Success across 22 contracts. The longest ran seven years and 8,440 hours on a single multi-tenant platform.
How engagements run: I do the engineering myself and stay the technical owner and point of contact throughout. When scope needs mobile, UI/UX, QA or DevOps specialists, I bring in people I've worked with for years rather than handing you to a project manager.
If you'd rather start with something fixed-scope, the projects below cover the usual entry points — a legacy code audit with a modernization roadmap and estimate, a custom API integration, an Angular admin dashboard, or ongoing support for an existing .NET system.
Steps for completing your project
After purchasing the project, send requirements so Serhii can start the project.
Delivery time starts when Serhii receives requirements from you.
Serhii works on your project following the steps below.
Revisions may occur after the delivery date.
Requirements & API review
Review API docs, clarify auth methods, rate limits, data mapping, and error scenarios before writing any code.
Integration development
Build the integration with error handling, retry logic, rate-limit compliance, and structured logging.