Senior Shopify Speed Expert — Heavily Customized Theme (Audit & Plan Required Before Any Work)

About the project: We run an established Shopify store with a heavily customized theme. We're looking for a senior Shopify performance developer to genuinely improve mobile loading speed — real, measurable speed, not cosmetic PageSpeed tricks. Important context (please read): our theme is complex and highly customized. Product pages, bundles, the cart, and a multilingual setup (~10 languages via Translate & Adapt) are all tightly interconnected. Changes that look simple have broken other parts of the site or other languages in the past. We are NOT looking for someone who installs a speed app and calls it done — we need someone who can understand a custom theme first, then optimize it safely. What we're looking for (this is the key part): Before doing ANY work on the site, you must: 1. Run a full performance audit. 2. Share a written plan: the specific issues found, the exact files/sections/templates you'll modify, what you'll change and why, and the current baseline scores. We will review and approve this plan before you touch anything. We're hiring the person who can prove — through the audit and plan — that they understand our setup and can work without breaking it. This vetting step is how we choose. Scope: - Improve real mobile loading speed, with priority on product pages (all languages), the add-to-cart button, and the cart page. - Target: 85+ mobile PageSpeed Insights measured on a product page and the cart page (not just the homepage). - Fix render-blocking JS/CSS, optimize Core Web Vitals (LCP, CLS, INP). - Image & asset optimization (WebP, responsive sizing, lazy load, LCP priority). - Preserve everything: design, tracking (Microsoft Clarity), conversion apps (OCU Upsells), bundles, cart logic, and all languages — tested and confirmed working after changes. Working method (required): - All work on a DUPLICATED theme. Nothing published to the live theme without our approval. - A theme backup taken before you start. - A final report: a change log file-by-file (what, where, why), before/after scores, confirmation that tracking and the full checkout/upsell flow work in multiple languages, and a "sensitive areas — do not touch" section for future devs. Who you are: - Senior Shopify developer specialized in heavily customized themes and advanced cart/bundle functionality — not a generic "PageSpeed optimizer." - Comfortable diagnosing and untangling custom Liquid code before optimizing. - Can explain your decisions clearly and document your work. To apply: Start your message with the word "AUDIT" so we know you read this post. Briefly describe how you'd approach the initial audit of a custom theme, and share 1–2 examples of speed work on complex/customized Shopify stores (before/after scores appreciated). Please don't send generic template proposals — they'll be ignored. Only work on fixed price not hourly