Corexy
S/05 — web development

Custom Web Applications on Next.js and TypeScript

Custom web application development means building the whole product that runs in a browser — interface, API, database, integrations, hosting — not assembling a template. We build client portals, internal dashboards, multi-tenant SaaS and admin panels on Next.js, TypeScript, NestJS and PostgreSQL. Teams call us at one of two moments: the first version, or a codebase someone else abandoned.

Discuss your taskFree scoping call, reply within 2 hours on business days

What this solves

The previous agency stopped replying

You have a repository, no developer, and no reliable account of what is inside it. We read the code, run it locally, document what it actually does, and tell you plainly whether it is worth continuing or rebuilding in parts.

Customers live in your inbox

Orders, statuses and documents are scattered across email threads and spreadsheets, and someone answers "where is my order?" by hand all day. A client portal puts it in one place, with roles and a change history.

Spreadsheets stopped scaling

Sheets break once twenty people edit them at once and you need permissions, validation and an audit trail. That is the point where an internal web app with a real database costs less than the workarounds around the sheet.

An MVP investors can actually click

You need a working product in front of first customers, not a Figma file. We ship a minimal version with real auth, payments and data, structured so version two extends it instead of replacing it six months later.

Reporting is a manual weekly ritual

The numbers sit in a database, an ad platform and an accounting system, and someone rebuilds the same summary every Monday. A dashboard with saved views and scheduled exports removes that job entirely.

How the work runs

  1. Scoping call

    1–2 days

    We walk through what has to work and for whom. You leave with a list of screens, an estimate in hours and a price band — free, no obligation, and yours to keep whoever you end up hiring.

  2. Data model and scope document

    3–5 days

    We map the screens and the database schema, then write down what is in scope and what waits for phase two. If you have no specification, we write one and you approve it.

  3. Two-week build cycles

    10 working days per cycle

    Every second week you get a staging URL rather than a status report: click through it and say what is wrong. Scope changes are priced before they enter the build, so the invoice never moves quietly.

  4. Hardening and launch

    3–5 days

    We run the flows, fix what breaks, set up the server, domain, backups and monitoring, then deploy to your infrastructure and hand over every credential.

  5. Handover and warranty

    1 day + 1 month warranty

    You receive the source code, deployment documentation and environment notes. For one month after release we fix bugs in delivered functionality at no charge.

Stack

We deliberately pick widely-known tools: the next developer you hire should be able to open the repository and be useful within a week. If you already run something in production, we work inside it instead of standing up a parallel stack next to it.

  • TypeScript
  • Next.js
  • React
  • NestJS
  • Node.js
  • PostgreSQL 16
  • Prisma
  • Redis
  • Docker
  • GitHub Actions
  • Caddy / Nginx
  • S3-compatible storage

What it costs

Client portal or internal tool

$1,500 – $4,000 / 150 000 – 400 000 ₽

Auth, roles, 5–10 screens, data entry, exports and one or two integrations. What moves the number up: fine-grained permissions, syncing with an ERP or accounting system, and business rules that have to be modelled properly rather than hard-coded.

SaaS MVP

$4,000 – $9,000 / 400 000 – 900 000 ₽

Marketing site, customer account, admin panel, billing and notifications — a version you can put in front of paying users. Six to ten weeks end to end. Native mobile apps and heavy analytics sit outside this band.

Dedicated engineer, monthly

from $400 / from 40 000 ₽ per month

A named engineer on your product: new modules, maintenance and incident response, billed against hours at $30/hour with a task report every two weeks. This is also how most project takeovers start, before anyone commits to a rebuild.

Prices are indicative and do not constitute a public offer. The final cost, scope and timeline are fixed in a contract or invoice after we have discussed the task.

Related case study

The clearest reference is a CRM we built from scratch for a large HoReCa service company: 12+ modules, 89 database migrations, and role-based access covering 9 roles across 87 permissions. Same stack and same two-week rhythm as described above, sustained over a long engagement rather than a one-off launch.

Read the KMD case

Frequently asked questions

How much does a custom web application cost?
$1,500–$4,000 for a client portal or internal tool, $4,000–$9,000 for a SaaS MVP. Every estimate is derived from a $30/hour rate, so it can be broken into line items and argued with. What actually moves the price is the permission model, the number of integrations and the screen count — not how ambitious the pitch sounds.
How long does it take to build an MVP?
Six to ten weeks from kickoff to a working version on your domain. A clickable staging environment with auth and the main flow exists by week two or three; the rest arrives in two-week increments. If you need it faster we cut scope, not testing, and we tell you exactly what is being cut.
Do we own the code and the infrastructure?
Yes. The repository lives in your GitHub organisation from day one, servers and domains are registered in your accounts, and the source code plus documentation transfer to you formally on full payment. There is no license, no runtime fee and no hosting we control on your behalf.
What stack do you build on and why?
Next.js and TypeScript on the front end, NestJS and PostgreSQL 16 behind it, Docker and GitHub Actions for deployment. It is chosen for hiring depth, not novelty: this is the stack with the largest pool of engineers who can take over from us. If your team already runs something else, we adapt rather than argue.
Can you take over a project another agency started?
Yes — it is a large share of the work we do. It starts with reading the repository and running it locally, after which you get a written account of what exists, what is broken and what it costs to move forward. Only then do we agree on whether to extend the codebase or replace it module by module.
What happens after launch — do you maintain it?
For one month after release we fix bugs in delivered functionality free of charge. After that you can take a monthly retainer from $400 with a dedicated engineer, buy hours as needed, or move everything in-house — we hand over the documentation and walk your developers through it. None of the three locks you in.
Do you work fixed-price or time and materials?
Both, depending on how well-defined the scope is. Clear boundaries get a fixed price and a fixed date; products still finding their shape run time and materials at $30/hour with a monthly cap so the budget cannot drift silently. Payment is 50% upfront and 50% on acceptance, in USDT (TRC-20/ERC-20) or by bank transfer.
How do you report progress and handle scope changes?
You get a staging URL every two weeks plus access to the task board and the repository, so progress is something you check rather than something you are told. New requests are estimated in hours and priced before work starts on them. The engineer writing the code is the person you talk to — there is no account manager in between.

Tell us what has to work

Send two paragraphs about the problem, or a link to a repository nobody is maintaining. You get a reply within two hours on business days, and an estimate in hours after one call.

Discuss your task
Next.js Web Application Development — Corexy