WordPress Custom Development: Themes, Plugins and Integrations

// Who is WordPress custom development for?

WordPress custom development is for businesses that have hit the limits of ready-made solutions. The need is usually simple, but no plugin does exactly that; combining three plugins slows the site, creates conflicts and adds a new risk with every update. If any of the following sounds familiar, you are on the right page, and the scoping call is free.

• 4 or 5 plugins are installed for one need and none does exactly what you want
• Data is carried by hand between the site and your accounting, CRM or stock software
• Customizations made to a ready-made theme disappear with every update
• You need a custom calculation, form flow or membership logic

We apply the same development discipline to corporate sites and WooCommerce stores; the code is always written update-safe.

// What is included and what is not

Development runs on a per-project basis. The table below lists what a standard project includes and what stays outside, line by line. If visual design is needed it is planned together with the web design team; development can also be done on top of an existing design, in which case no design item enters the quote at all, and we state that rule from the start.

For those who want ongoing maintenance, a maintenance plan is recommended separately after development.

// How does it work and how long does it take?

The process has five steps. A small plugin takes 3 to 5 business days, an integration project 2 to 4 weeks; the duration is written in the specification and no code is written until it is approved. Bugs that appear within 30 days of delivery are fixed free of charge and the output of every step is shown to you.

// How is the price determined?

Three variables set the price: complexity of the function, number of external systems to integrate and whether an interface is needed. A single calculation form and a two-way CRM integration do not carry the same workload, so we quote from the technical specification rather than a fixed list. The scoping call is free and the quote is fixed once the specification is approved.

The price does not rise during development. If the scope changes, the extra work is written up separately and never done without approval. The source code is yours; there is no licence or annual fee. Payment is split across delivery milestones.

// Results we have delivered

The three cases below represent different types of development. We do not share client names without permission, so sector and scale are given instead; figures come from Zep Bilisim delivery reports. In all three, the project started with ready-made plugins, moved to custom code when the limit was hit, and had no problems in later updates.

• Insurance agency — 5 plugins installed for a quote calculator were replaced by one custom plugin; page weight fell 58% and form submission errors went to zero
• Wholesaler, 2,000 products — A two-way API connection was written between the stock system and WooCommerce; 2 hours of daily manual stock entry disappeared
• Education provider — Customizations lost with every update of a ready-made theme were moved to a child theme; no post-update breakage in 2 years

The difference between doing a job with 5 plugins and with 200 lines of custom code is not page speed; it is whether the site still works two years later.

// The team behind the work

Development is carried out by Caner Zep Çelik, founder of Zep Bilisim. As founder and technical consultant he has worked on WordPress development, API integrations and software architecture since 2020 and has been involved in more than 100 projects. He writes the technical specification and sets the code architecture himself and does not outsource the work.

The delivery document is written by the same person: where the code lives, what it does, where each setting is changed and what to watch during updates. The document lets another developer take over the code if you ever work with someone else.

// When is it not needed?

If one well-known plugin fully covers the need, writing custom code is wasted money; we say so in the scoping call and recommend the plugin. A custom theme is not needed for colour, font or layout changes either; a few hours with a child theme is enough, and we say that plainly too.

If the need stretches beyond what WordPress is for, such as a full enterprise application or a mobile-app backend, we point you to custom software development.

For store-focused development see WooCommerce support, and for needs beyond WordPress see custom software development. If you want to measure the speed effect of the custom code, the measurement method on speed and performance optimization applies. WordPress's official plugin developer handbook describes the coding standards and hook architecture we follow.

// Frequently Asked Questions