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BigTree108

Software architecture and fractional CTO services

Software architecture consulting and fractional CTO services: solution architecture for fintech, SaaS and e-commerce systems, cloud, data and AI architecture, security architecture, architecture reviews, technical due diligence, modernisation plans and part-time technical leadership, with software architects for your team or a defined engagement.

What our software architects do

  • Fintech and payments architecture

    The system of record for money decided first, then consistency between the ledger and every payment provider through outbox messages and reconciliation jobs, card data kept out of PCI DSS scope by tokenisation, and recovery targets that meet DORA and your regulator.

  • Data and AI architecture

    The data platform laid out end to end: operational and analytical stores, streaming and change data capture between them, data contracts and an owner for each domain, and where language-model retrieval and evaluation sit, sized for what the data costs to store and query.

  • SaaS platform architecture

    The tenancy model and its migration path as customers grow, regional deployments for data residency, public APIs, webhooks and extension points customers can build on, and a written rule for when a module becomes its own service.

  • E-commerce and marketplace architecture

    Composable commerce with the catalogue, search, cart, checkout, payments and order management as separate services, stock that stays consistent across channels, and a platform load-tested for peak sales days.

  • Cloud architecture and cost

    Workloads placed on Azure, AWS or Google Cloud against reliability targets and a monthly budget, managed services weighed against self-run ones, and the bill broken down by product and environment.

  • Security architecture

    Threat models for each system, identity and zero-trust access design, encryption and key management, and logging that answers who did what, so an ISO 27001, SOC 2, PCI DSS or HIPAA audit finds the controls already in the design.

  • Architecture reviews and modernisation plans

    A read-only review of the code, the infrastructure and the delivery pipeline that ends in a written list of risks in order of impact, and a route to the system you need that replaces parts behind stable interfaces one at a time rather than in a rewrite.

  • Technical due diligence

    An assessment before an investment or acquisition: code quality, security, scalability, dependency licences, running costs and how much of the system only one person understands.

  • Fractional CTO

    Part-time technical leadership: the roadmap, build-or-buy calls, cloud and vendor choices, engineering rules and first hires, and a technical voice in board and investor meetings.

Hire software architects

  • Dedicated software architects

    Software architects who join your team full time, work in your tools and process, and report to your lead. You interview them; we carry the Ukrainian contract, payroll, invoicing and leave.

  • Software architecture projects

    A defined piece of software architecture with a scope, a fixed plan and a named lead on our side who owns the result and reports progress in your channels.

  • Ongoing software architecture

    Software architecture as a continuing service: the same people every month, a backlog you prioritise, and hours you can see in our portal and on the invoice.

The dedicated team page explains how specialists join your team, and the outsourcing page covers project delivery, take-overs and how we charge.

Who works on your software architecture

  • Software and solution architects

    System design, reviews and modernisation plans

  • Fractional CTOs

    Roadmap, technology choices and team building

  • Cloud architects

    Azure, AWS and Google Cloud infrastructure and running costs

  • Data and AI architects

    Data platforms, streaming and language-model systems

  • Security architects

    Threat models, identity and compliance controls

How we approach architecture

Every significant decision is written down as an architecture decision record with the options considered and the reason for the choice, so the next engineer can see why as well as what. We favour well-supported, current technology, a modular monolith until the team or the load calls for separate services, and managed services before self-run ones, and every recommendation comes with what it will cost to build and to run.

The practices we recommend are the ones we run: everything as code with Terraform and GitHub Actions on federated credentials, tests with every feature, zero warnings, security advisories as unconditional upgrades, secrets only in Key Vault, deny-by-default firewalls, Always Encrypted columns for personal and financial data, CodeQL on every push and drift detection.

Other specialised development we provide

Specialised development overview

Questions about software architecture and fractional CTO services

What does a fractional CTO do?

The work of a CTO for a set number of days a week: owning the technical roadmap, making build-or-buy and vendor decisions, reviewing the architecture, setting up how the team builds and releases, and hiring the first engineers, with interview loops from a company where nineteen people are active technical interviewers. It suits a company whose technology matters but which is not yet ready for a full-time CTO.

Which industries do your software architects work in?

Most often fintech, banking and insurance (payments, ledgers and lending platforms), data and AI products (data platforms and language-model features), SaaS and enterprise software (multi-tenant platforms and ERP integrations), healthcare (patient data, HL7 FHIR integrations and privacy controls), e-commerce and marketplaces (commerce platforms built for peak traffic) and cybersecurity. They also work on travel and hospitality booking systems and cloud infrastructure products.

What do we receive from an architecture review?

A written report: how the system is built, the risks in order of impact, what each would take to fix, and a recommended order of work. Nothing in your system is changed during the review, because access is read-only.

Can you review a system another company built?

Yes. We have taken over nine systems from other teams so far, the oldest written in 2008. A take-over starts with a read-only review and a written list of risks, and so does every review we do for a client.

How quickly can software architects start?

When the right software architect is available, the start is gated only by your interview and the NDA and IP assignment. Otherwise we run a search, which typically produces candidate profiles within two to three weeks, and nobody starts until you have said yes.

How do we hire software architects through BigTree108?

Tell us the work, the seniority and the hours you need. We propose one or two people with their profiles, you interview them the way you would interview your own hire, and you sign one agreement with BIG TREE 108 LLC and receive one invoice a month.

Who owns the work they produce?

You do. Every specialist has a signed contract with BigTree108 that assigns all work product to the company, and our agreement with you assigns it onward. Code, designs and documents are delivered into your own repositories and tools, not kept where only we can change them.

Need senior technical judgement?

Tell us about the system, the team and the decision ahead. You get an answer within one business day: a proposal for the review, a plan for the work, or the profile of the architect who would lead it.

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