# Ecommerce Performance and Reliability Troubleshooting > When a store slows down or behaves unexpectedly, the most effective approach is to start with the affected time, customers and page step, then compare a failing request with a healthy one before changing caches, servers or code. Evidence gathered before any change makes the diagnosis accurate and the fix reversible. - Type: Merchant guide - Level: Intermediate - Reading time: About 9 minutes - Audience: Written for store owners, builders, and designers refining high-performance ecommerce stores. - Last updated: 2026-11-04 - Canonical page: https://academy.getzenbasket.com/merchant-questions/ecommerce-performance-and-reliability-troubleshooting/ - Part of: [Merchant Questions](https://academy.getzenbasket.com/merchant-questions/) on ZenBasket Academy --- ## What you need to know ### Why is my ecommerce homepage slow? A slow homepage is commonly caused by a delayed server response, oversized hero media, too many featured sections or third-party scripts. Compare its loading waterfall and LCP element with a healthy page. ### Why are product pages slow? Slow product pages often involve main images, variant or stock APIs, reviews, recommendations and accumulated app code. Test one affected product against a simple product to isolate data and feature differences. ### Why are category pages slow? Slow category pages may request too many products and images, run costly filters or sorting, or render too many cards at once. Measure server query time, response size and browser rendering separately. ### Why is ecommerce search slow? Search may slow because the index is overloaded, queries are expensive, filters are broad or result enrichment calls other services. Trace one slow query and compare it with a fast query of similar intent. ### Why is Add to Cart slow? Add to Cart may wait on inventory, pricing, promotion, session or database work, or the browser may be blocked by JavaScript. Trace from the button event to the confirmed cart change and visual response. ### Why is checkout slow? Checkout may be slow because address, tax, shipping, inventory, fraud and payment calls run in sequence or fail slowly. Time each step and remove optional work from the critical path. ### Why are APIs timing out? APIs time out when processing, dependencies or queueing exceed the caller's limit, often under load. Review slow traces, resource saturation and downstream timing before simply increasing the timeout. ### Why is the database slowing down? The database may slow because a deployment changed a query, data volume grew, an index disappeared, locks increased or capacity became saturated. Compare query plans and waits before and after the slowdown began. ### Why is my store slow only during high traffic? High-traffic-only slowness points to a capacity, contention, quota or cache-efficiency limit. Correlate throughput with latency, errors, connections, queue depth and provider throttling to find the first saturated layer. ### Why is my store slow only in certain countries? Country-specific slowness points to network distance, weak CDN coverage, wrong origin routing or a regional third-party service. Test the same page from affected and healthy regions and compare cache and connection timing. ### Why are background jobs delayed? Jobs become delayed when arrival exceeds processing, workers fail or pause, a dependency slows or one message blocks a partition. Check the age of the oldest job, rates, failures and worker health. ### Why are customers seeing stale prices or inventory? Customers see stale price or inventory when cache or search updates lag behind the authoritative record. Follow one product change through every event, cache and index until the old value is located. ### Why are orders being processed twice? Orders are processed twice when requests, events or jobs are retried without a stable idempotency key or unique business constraint. Identify the shared original attempt and close every duplicate entry path. ### Why does checkout fail intermittently? Intermittent checkout failure often depends on a payment method, product, address, device, provider instance or traffic level. Group failures by exact step and correlation ID instead of averaging them together. ### Why did the store go down during a promotion? A promotion outage usually exposes an untested demand estimate, shared bottleneck, provider quota, cache stampede or retry surge. Reconstruct the timeline from the first saturation signal and confirm why protection did not engage. ### How do I perform an ecommerce performance audit? Inventory important page types and customer actions, collect field and lab data, trace network and browser work, inspect APIs and databases, audit third parties and rank findings by customer impact. Establish a baseline and verify each change against it. ### How do I perform an ecommerce reliability audit? Map critical journeys and dependencies, review availability and error objectives, test failure handling, queues, idempotency, monitoring, backups and disaster recovery, then run controlled exercises. Rank gaps by customer harm, data risk and recovery difficulty. ### A quick store check For one current incident, record impact, start time, last change, evidence, suspected layer, safe mitigation and proof of recovery. --- ## Frequently asked questions ### Should I change several systems during an incident? Prefer one safe, reversible mitigation at a time when possible, and record each change so its effect can be measured. ### When is a performance incident closed? After customer impact has ended, data is reconciled, monitoring confirms stability and the cause and follow-up actions are documented. --- ## Related learning path - **Ecommerce Disaster Recovery and Business Continuity** - **Ecommerce Analytics Troubleshooting and Audit** - **Order, Return and Support Troubleshooting** - [ZenBasket Build Guide](https://help.getzenbasket.com/zenbasket-builder/)