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YionStack
Sub-processor register · UK GDPR Article 28

Every third party who touches your data.

This is the canonical, public list of sub-processors Yiontech LTD engages to deliver YionStack. Every entry has a written data-protection agreement, a known region, and a documented transfer safeguard. The change-log at the bottom is the authoritative record of additions and removals.

Version
v1.1
Effective
11 May 2026
Total vendors
12
Notice period
30 days

Article 28(2) commitment

We will not engage a new sub-processor without giving you 30 days' notice via the change-log below and an email to the controller contact on your account. Object in writing within those 30 days and we will work with you to find a path forward.

UK / EEA-first

Every vendor we can keep in the UK or EEA, we do. Where a vendor is US-based (LLM providers, Postmark) we use SCCs with the UK Addendum (IDTA) and the vendor's most data-minimising tier — typically zero-retention APIs.

Subscribe to changes

Email subprocessors@yionstack.co.uk to receive an email the day we publish a change. The list itself is also versioned in this page's source so legal teams can diff it over time.

Active sub-processors

12 vendors · grouped by category
  • Google Cloud (UK / EU regions)

    Application hosting, database (Cloud SQL Postgres), object storage, queue infrastructure

    CategoryInfrastructure
    RegionUnited Kingdom · europe-west2
    TransferNo outbound transfer — data stays in the UK region
  • Cloudflare

    DNS, CDN, edge caching, WAF, DDoS mitigation, bot management

    CategoryEdge / network
    RegionGlobal edge · UK PoPs prioritised
    TransferIDTA + Cloudflare Data Processing Addendum (UK Addendum to EU SCCs)
  • Cloudflare R2

    Object storage for user-uploaded files (images, PDFs, design exports)

    CategoryStorage
    RegionCloudflare automatic distribution · default ENAM/EEUR
    TransferIDTA + Data Processing Addendum
  • Stripe Payments UK Ltd

    Card / direct-debit processing, billing, tax calculation, customer portal

    CategoryPayments
    RegionUnited Kingdom (controller for payment data)
    TransferUK GDPR Article 28 + Stripe Data Processing Agreement
  • Postmark (ActiveCampaign)

    Transactional email (magic links, receipts, system notifications)

    CategoryEmail
    RegionUnited States · Postmark EU region opt-in available
    TransferEU SCCs + UK Addendum (IDTA)
  • OpenAI, L.L.C.

    Large-language-model inference for the YionAI operator

    CategoryAI / inference
    RegionUnited States · zero-retention API
    TransferEU SCCs + UK Addendum · OpenAI Enterprise DPA · 0-day retention enabled
  • Anthropic, PBC

    Large-language-model inference for the YionAI operator (fallback / Claude tier)

    CategoryAI / inference
    RegionUnited States · zero-retention API
    TransferEU SCCs + UK Addendum · Anthropic Commercial Terms · 0-day retention enabled
  • BetterStack

    Uptime monitoring, public status page, on-call alerting

    CategoryObservability
    RegionEuropean Union · Frankfurt
    TransferNo outbound transfer — EU-hosted
  • Sentry (Functional Software, Inc.)

    Application error monitoring, release tracking

    CategoryObservability
    RegionEuropean Union region (sentry.io eu1)
    TransferEU-hosted; SCCs in place for any incidental US support access
  • Yiontech personnel & contractors located outside the UK

    Yiontech personnel and contracted staff based outside the UK who access personal data to do their jobs — currently customer-support handling (phone, email, chat, tickets) and the related in-product support access, and operational / platform support tasks where required

    CategoryPersonnel · all roles
    RegionOutside the UK (specific country named in our IDTA & Transfer Risk Assessment — available to customers on request)
    TransferUK IDTA + completed Transfer Risk Assessment for the destination country · supplementary measures: encryption in transit & at rest, role-based access + row-level data isolation, access logging, data minimisation, managed-device controls, written data-protection & confidentiality undertaking
  • Companies House (Crown — UK Government)

    Director and registered-address lookups during business onboarding

    CategoryUK government data
    RegionUnited Kingdom
    TransferNo transfer — public-register data, UK Crown
  • HMRC (Crown — UK Government)

    Making Tax Digital VAT submissions and registration checks

    CategoryUK government data
    RegionUnited Kingdom
    TransferNo transfer — direct HMRC API; OAuth2 user consent

The “Yiontech personnel & contractors located outside the UK” entry covers everyone who works for us from outside the UK in any role that involves seeing personal data — today that is customer support (and the in-product support access that goes with it) and operational / platform support where it is needed; any other role or country is covered by the same framework and listed here when it is added. Whenever a team member outside the UK looks at a record, that is a restricted transfer under UK GDPR Chapter V, and it is governed by the same machinery as any other non-UK processing in this list: the UK International Data Transfer Agreement, a completed Transfer Risk Assessment for the destination country, and a set of supplementary measures — data stays on UK / EEA infrastructure and is accessed record-by-record through the product (no bulk export), every access is logged, role-based access plus row-level isolation means a person only ever sees data for the businesses or systems their role covers, data is minimised, and the person works from a managed device under a written data-protection and confidentiality undertaking. If a team member is engaged as an independent contractor they are a sub-processor under our DPA; if engaged directly by Yiontech they are personnel — either way the transfer safeguard and the supplementary measures are the same.

Change-log

Every change to the list above appears here, oldest at the bottom.

Subscribe by email
  1. 2026-05-11v1.1

    Added "Yiontech personnel & contractors located outside the UK" — Yiontech personnel and contracted staff based outside the UK who access personal data to do their jobs, currently customer-support handling and the related in-product support access, and operational / platform support tasks where required. Any future role or destination country is covered by the same framework and added here with notice. Transfers are safeguarded by the UK International Data Transfer Agreement and a completed Transfer Risk Assessment for the destination country, with supplementary technical and organisational measures (encryption in transit & at rest, role-based access + row-level data isolation, access logging, data minimisation, managed-device controls, written data-protection & confidentiality undertaking). The specific destination country is named in those documents and is available to customers on request. Notice period applies as set out above.

  2. 2026-04-26v1.0

    Initial publication of the sub-processor register. All vendors listed were in use at launch — this is not a notification of new vendors, this is the baseline.