I recently integrated the eBay API into my website to synchronize product listings, inventory status, and order information automatically between my platform and eBay store. Initially, everything worked correctly and updates appeared almost instantly across both systems without any noticeable delays. However, after traffic on my website started increasing, the API synchronization became unstable and inconsistent during normal operation. Some products update successfully while others remain outdated for hours even though the API requests appear to complete normally. In several cases, inventory quantities displayed on my website no longer match the actual stock levels shown on eBay. The strange part is that the problem does not happen continuously and seems to appear randomly throughout the day. Sometimes order details synchronize perfectly for multiple transactions in a row, but then newer orders suddenly fail to appear until the sync process is restarted manually. I checked my API logs and occasionally noticed delayed responses, incomplete payload data, and intermittent timeout warnings during higher traffic periods. Despite this, the API credentials remain valid and authentication requests continue working correctly without expiration issues. Because the failures are inconsistent, reproducing the exact conditions causing the problem has become extremely difficult. I originally suspected server resource limitations or database bottlenecks on my side, so I upgraded hosting resources and optimized background processing tasks. Although these improvements reduced response times slightly, they did not eliminate the missing inventory updates and delayed order synchronization. I also implemented request queues and retry handling to prevent failed API calls from being skipped completely. Even with those safeguards in place, some listing updates still disappear randomly without generating clear error responses. The most confusing detail is that the same API operations work perfectly inside testing environments but become unreliable under live production traffic. Another issue I observed is that inventory synchronization becomes less stable whenever multiple users browse product pages simultaneously. During traffic spikes, API requests occasionally take much longer to process and some product data sections remain stuck showing outdated information. In a few situations, orders created successfully on eBay were not reflected on my website until several hours later despite repeated sync attempts. I checked server logs, firewall settings, and database performance metrics, but there are no obvious hardware or network failures during the incidents. This makes me wonder whether API rate handling or concurrent request behavior could somehow be involved. Mobile visitors appear to experience the issue more often than desktop users, especially when products are updated frequently during active browsing sessions. Some users report seeing available stock quantities that later change unexpectedly during checkout because the website failed to receive updated inventory information in time. Others mention that newly added eBay listings appear partially loaded with missing images or outdated pricing details. I tested the synchronization system across different browsers and devices, but the inconsistency remains regardless of frontend environment. Because of this, I am unsure whether the issue originates from backend API processing or asynchronous data handling on the website itself. At this stage, I would genuinely appreciate advice from developers or sellers who have integrated eBay APIs into medium or high-traffic websites. I am trying to understand whether these random synchronization failures are usually related to API rate limits, webhook delays, concurrent processing conflicts, or incorrect handling of inventory update requests. My goal is simply to maintain accurate product and order synchronization without causing delays or inconsistent inventory information for customers. If anyone has experienced similar intermittent API sync failures, delayed order updates, or unreliable inventory refresh behavior under increasing traffic, I would really appreciate guidance on the best direction for debugging and long-term stabilization.
