Backend and API Development
The data model, business logic and documented APIs behind your application — the part users never see directly but that every screen, app and integration depends on. GullySystem builds it to stay fast and correct as your records grow.
Overview
The backend is where your business rules actually live: how a rate is calculated, what an approval requires, how stock is reserved against an order. An API is the documented way other things — your web app, your mobile app, a partner system — read and write that data safely. This page covers building that layer on its own, separate from the interface built on top of it.
When to Scope This Separately
- One backend needs to power a web application, a mobile app and a customer portal, all built on the same data
- You already have a frontend or an in-house team that will build the interface, but need the backend engineered properly
- A partner or franchise needs a documented API to integrate their own systems with yours
- Your current backend logic lives scattered across spreadsheets, scripts and one person's memory
What Goes Into the Backend Build
Data Modelling
A database structure that matches how your business actually relates customers, orders, items and accounts, built to stay correct as volume grows.
Business Logic and Validation
Rate calculations, approval rules and status transitions enforced consistently, not re-implemented differently in every screen that touches them.
Documented REST or GraphQL APIs
A clear, versioned API surface with documentation any developer — ours or yours — can build against without guessing.
Authentication and Rate Limiting
Secure access for internal apps and external partners, with usage limits so one integration cannot overload the system.
How This Fits With Other Builds
This backend typically becomes the foundation for the web application, mobile application or customer, vendor and dealer portal described on their own pages. Scoping and building it first, with a clear API contract, lets those interfaces be built or rebuilt independently without disturbing the data and logic underneath.
Frequently asked questions
Do we need the backend built separately from the frontend?
It is worth scoping separately when more than one application will run on the same data — a web app and a mobile app, for instance — or when you already have frontend capability and just need the data layer engineered properly. For a single, simple application, backend and frontend are usually built together.
What drives the cost of a backend and API build?
How complex the business rules and calculations are, how many entities and relationships the data model covers, how many applications and external systems will consume the API, and how much historical data must be modelled and migrated.
What decides how long the backend takes to build?
The complexity of the business logic being encoded, the number of integrations the API needs to support at launch, and how much of the data model already exists in a documented form versus needing to be reconstructed from spreadsheets and habit.
Can our existing frontend or app connect to a new backend?
In most cases, yes. We design the API to match what your existing frontend or app already expects to send and receive, or agree a migration plan with your team where the interface has to adjust.
How do you keep the API secure for outside integrations?
Access is controlled through authenticated API keys or tokens scoped to what each integration actually needs, requests are rate-limited, and all activity is logged, so a partner integration cannot reach or overload data outside its scope.
Who owns the backend, the database and the API documentation?
You do. The source code, database design and API documentation are handed over in full, and the API can be extended or consumed by any team afterwards, not only by us.
What do you need from us before this begins?
A description of your core business entities and rules, a list of every application or system that will need to read or write this data, and sample data or documents that show how records are currently structured.
Tell us what you need.
Send a short brief and one of our engineers will come back to you — usually the same day.
- No obligation
- We reply the same working day
- Your details stay private