# Slow fetching performance **URL:** \ **Category:** OpenSearch\ **Tags:** troubleshoot\ **Created:** [May 16, 2025, 6:38pm UTC](https://forum.opensearch.org/t/slow-fetching-performance/24423 "2025-05-16T18:38:50Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![daniel2025](https://avatars.discourse-cdn.com/v4/letter/d/a88e4f/32.png) [@daniel2025](https://forum.opensearch.org/u/daniel2025)\ **Post date:** [May 16, 2025, 6:38pm UTC](https://forum.opensearch.org/t/slow-fetching-performance/24423/1 "2025-05-16T18:38:50Z")
**Versions** (relevant - OpenSearch/Dashboard/Server OS/Browser): OpenSearch 2.17 and OpenSearch 2.19 **Describe the issue** : Slow fetching performance **Configuration** : AWS OpenSearch Service 3 Dedicated Master nodes: r7g.4xlarge 39 Data nodes: i4g.4xlarge 1116 primary shards 2 replicas Most shards are between 10-50 GB (some are smaller) ~1 billion documents **Relevant Logs or Screenshots** : Query performance is good when size=0 but when size=1 and \_source=false the query time increases significantly. Only the meta fields are being returned, no \_source or stored fields. Query: ```auto { "query": { "query_string": { "query": "the OR a OR is OR in OR at OR on" } } } ``` \_count for the above query is 1,057,557,417 Performance with size = 0 (\_search?\_source=false&request\_cache=false&size=0) ```auto Type Name # reqs # fails | Avg Min Max Med | req/s failures/s --------|----------------------------------------------------------------------------|-------|-------------|-------|-------|-------|-------|--------|----------- search /_search - size=0 51 0(0.00%) | 187 158 440 180 | 0.86 0.00 --------|----------------------------------------------------------------------------|-------|-------------|-------|-------|-------|-------|--------|----------- Type Name 50% 66% 75% 80% 90% 95% 98% 99% 99.9% 99.99% 100% # reqs --------|--------------------------------------------------------------------------------|--------|------|------|------|------|------|------|------|------|------|------|------ search /_search - size=0 180 190 190 190 200 210 260 440 440 440 440 51 --------|--------------------------------------------------------------------------------|--------|------|------|------|------|------|------|------|------|------|------|------ ``` Performance with size = 1 (\_search?\_source=false&request\_cache=false&size=1) ```auto Type Name # reqs # fails | Avg Min Max Med | req/s failures/s --------|----------------------------------------------------------------------------|-------|-------------|-------|-------|-------|-------|--------|----------- search /_search - size=1 11 0(0.00%) | 14508 11888 17015 15000 | 0.06 0.00 --------|----------------------------------------------------------------------------|-------|-------------|-------|-------|-------|-------|--------|----------- Type Name 50% 66% 75% 80% 90% 95% 98% 99% 99.9% 99.99% 100% # reqs --------|--------------------------------------------------------------------------------|--------|------|------|------|------|------|------|------|------|------|------|------ search /_search - size=1 15000 15000 16000 16000 16000 17000 17000 17000 17000 17000 17000 11 --------|--------------------------------------------------------------------------------|--------|------|------|------|------|------|------|------|------|------|------|------ ``` Any help would be appreciated. Let me know if any additional information is needed. Thanks