Software & Automation

Custom API Development

Custom API development creates a documented backend for your own data model and business rules, rather than merely connecting to an existing third-party service.

  • Delivery7-40 days
  • RevisionsPackage dependent
  • PricingQuoted by scope
Get a quote Choose the right level of scope

What this service covers

A new API defines resources, endpoints, data contracts, errors, and permissions for web, mobile, or system clients. This differs from REST API Integration, which connects existing software to endpoints already provided by another company.

Using FastAPI or Node.js, I can implement database access, validation, role-based authorization, error handling, rate limits, logs, tests, and OpenAPI documentation. Controls are selected from the risk model; secrets management, updates, monitoring, and independent security testing remain ongoing responsibilities.

Capacity targets are based on expected request volume and verified with agreed load tests. Unmeasured traffic cannot receive an absolute performance guarantee, and results depend on database queries, infrastructure, and external dependencies. Hosting, maintenance, and support terms are listed in the proposal.

What's included

  • API resource and endpoint design
  • Authentication and role-based authorization
  • OpenAPI endpoint documentation
  • Deployment and technical handover

Tools and platforms

PythonFastAPINode.jsPostgreSQL

How the project works

  1. 01

    Scope

    We define the objective, deliverables, dependencies, and success criteria before production starts.

  2. 02

    Build

    You review working previews, so decisions are made against tangible output.

  3. 03

    Refine

    The agreed revision rounds are used to complete details within scope.

  4. 04

    Handover

    I deliver the agreed files, access, and practical usage notes in an organized package.

Software & Automation · Delivery

Choose the right level of scope

Final pricing is provided after scope, deliverables, and integrations are confirmed.

Starter

Core service

A small API with a limited endpoint set.

  • Core endpoints
  • Simple database model
  • Authentication
  • Concise documentation
Delivery: 7-12 days Revisions: 1 round
Growth

Application API

A documented API for a multi-screen application.

  • Expanded endpoint set
  • Roles and authorization
  • Detailed OpenAPI documentation
  • Validation and error handling
  • 2 revision rounds
Delivery: 13-22 days Revisions: 2 rounds
Advanced

Scalable backend

A proposal-defined API with measured capacity targets.

  • API architecture defined in the proposal
  • Advanced controls and rate limiting
  • Approved external integrations
  • Monitoring and structured logs
  • Deployment and scaling plan
  • 3 in-scope revision rounds
Delivery: 22-40 days Revisions: 3 rounds

Frequently asked questions

How long does custom API development take?

Estimated delivery is 7-40 days, based on endpoints, data models, permissions, integrations, and tests. External access and security review can affect the schedule.

Will you provide API documentation?

Yes. I provide OpenAPI documentation for the approved endpoints, including request models, responses, authentication, and common errors.

Can the API support my mobile application?

Yes. A documented JSON-over-HTTP contract can support web and mobile clients. Client versions, authentication, offline behavior, and network conditions are verified during integration testing.

REST API Integration

REST API integration connects your existing application to documented payment, shipping, messaging, accounting, CRM, or other authorized services.

Webhook Integration

Webhook integration handles payment, order, form, or other events using signature verification, duplicate protection, queues, and defined retry rules.

Custom Software Development

Custom software development turns well-defined internal workflows into a scoped web, desktop, or hybrid application when packaged tools are not a practical fit.

Custom Script Development

Custom script development is suited to narrow, repeatable tasks such as file organization, format conversion, backups, and scheduled processing.

Python Script Development

Python script development is ideal for processing, validating, combining, and reporting on Excel, CSV, and other tabular data.

Business Process Automation

Business process automation connects approved steps and systems while preserving required human decisions, logs, alerts, and recovery paths.

Get a quote for Custom API Development.

Share a short brief and I’ll help define the scope, dependencies, and a realistic delivery window.

Tell me about the project