Logz.io conducted an internal benchmarking study to determine the most effective way to utilize Elasticsearch clusters on AWS, focusing on indexing performance. They developed a custom stress test tool to simulate their specific logging use case and tested various instance types, including those with ephemeral storage and EBS (Elastic Block Store). Despite Elastic's advice against using EBS, the SSD-backed EBS performed exceptionally well, especially when instances were EBS-optimized. The study highlighted the importance of calibrating bulk sizes and revealed that while the c4.2xlarge instance was more cost-effective, the m4.2xlarge offered more RAM, which is crucial for Elasticsearch performance. Ultimately, Logz.io concluded that the m4.2xlarge was the best fit for their needs, emphasizing that the choice of instance type depends on specific use cases and infrastructure requirements.