Maxim Mironjuk
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September 06, 2025
An initial catalog load with several million product documents runs noticeably slower under Elasticsearch's default settings than the underlying hardware could actually deliver. The bulk API itself is rarely the bottleneck, it is the interplay of batch size, refresh interval, replica count, and thread pool configuration, which under default values is tuned for balanced continuous operation, not for a short, intensive bulk import. This article shows how to systematically determine the optimal batch size, which temporary setting changes have the biggest effect during a bulk load, and what a practical tuning checklist looks like for the initial indexing of a large catalog.