PrestaShop 8 to 9.1 Clean Migration: Data, SEO, Perform. Staging

I am looking for an experienced PrestaShop specialist to migrate an existing PrestaShop 8.2 store to a clean PrestaShop 9.1 installation.

The goal is not simply to copy the old database. I want a clean, stable, fast and maintainable PS9 store while preserving essential business data and SEO.

Live store: www.oxiwhite.nl

The PS8.2 shop must remain live during the project. The new shop should be built and tested on a staging domain on my own hosting account before go-live.

MIGRATION SCOPE
Please migrate:

Products, combinations, attributes and features
Categories and relationships
Manufacturers/brands, including logos/images and product associations
Product/category images and associations
Stock, SKU/reference/EAN data
Prices and relevant specific prices/discounts
Customers, addresses and customer groups
Existing customer password/login compatibility
Historical orders, order details and statuses
CMS pages/content
Meta titles/descriptions
Existing friendly URLs/link_rewrite
Other essential core store data

Existing customers must be able to log in with their current email/password without a reset.

LANGUAGE
The source store is Dutch. Dutch language records and associations must be mapped correctly. Do not import or activate other languages unless agreed beforehand.

SEO
Before migration, export the existing relevant URLs and compare them with the new store afterwards. Existing URLs should remain identical wherever technically possible. If a URL must change, create a direct 301 redirect to the correct replacement page.

Before launch, check 404s/broken links, canonicals, XML sitemap, robots.txt, metadata, redirects and general technical SEO.

MIGRATION METHOD & VALIDATION
I do not want PS8 database tables simply copied or blindly merged into PS9. Data, IDs, language records and relationships must be properly mapped and validated for the PS9 structure.

Please explain how you perform and validate a PS8 → PS9 migration.

Validation should include record counts and important relationships for products/combinations, categories, brands, customers/addresses, orders, images, stock and SEO/URL data. I do not want to discover missing or incorrectly linked data manually afterwards.

FINAL DELTA SYNC
Because the PS8 shop remains live during development, a final delta sync is required immediately before go-live. This must include all new customers, addresses and orders created after the initial migration, plus other agreed changed data.

Please explain how you perform this sync without overwriting completed work in the new store.

PERFORMANCE
Before launch, check caching/configuration, PHP/server errors, JavaScript errors, mobile usability, image optimisation, frontend performance and Core Web Vitals/PageSpeed. I do not expect unrealistic PageSpeed 100 scores, but the shop should be technically healthy and well optimised.

THEME & MODULES
I intend to use a new PS9-compatible theme. Please state whether theme installation/configuration is included.

I can provide/purchase replacement modules where needed. Do not migrate old incompatible modules unnecessarily or add/replace modules without discussing them with me first.

DATABASE/HOSTING CLEANUP
There are several databases from the live shop, staging installations and a previous unsuccessful migration.

Please:

Identify which database belongs to which installation
Confirm which are active
Create backups where needed
Identify obsolete/unused databases
Remove unused databases/users only after confirmation

Nothing should be deleted blindly.

I would also like the current PS8 database checked for unnecessary bloat (logs/statistics/obsolete module data), but only where this can be cleaned safely without affecting products, customers, orders, stock or SEO.

STAGING & GO-LIVE
The new store must be completed and tested on staging first. Before launch, create a full backup/rollback point.

Go-live should only happen after migration validation, customer login, checkout, orders, images/content, SEO URLs/redirects and core functionality have been tested, and the final delta sync is complete.

YOUR PROPOSAL
Please include:

Experience specifically with PS8 → PS9 migrations
Examples of similar migrations
How you map/migrate database data
How you validate data and relationships
How you preserve customer passwords
How you perform the final delta sync
How you protect SEO URLs/rankings
Whether theme setup is included
Estimated timeline
Fixed price for the complete scope

I have deliberately not specified a target budget. Please provide your own fixed-price quotation so I can compare proposals based on approach, PrestaShop experience, scope, timeline and price.

Please do not apply if your approach is simply to copy/merge PS8 database tables into PS9 without proper mapping and validation. I am looking for a properly validated, SEO-safe, stable and high-performing PrestaShop 9 store.