Cold Scan Latency
Slow first-query performance against S3-stored data, caused by object discovery, metadata fetching, and data transfer over HTTP.
Summary
Slow first-query performance against S3-stored data, caused by object discovery, metadata fetching, and data transfer over HTTP.
Cold scan latency is the fundamental performance trade-off of the separation of storage and compute pattern. Every query against S3 starts with network overhead that does not exist when querying local disk.
- Cold scan latency is not the same as S3 being slow. S3 throughput is high, but initial latency per request is ~50-100ms. For queries touching many files, this adds up.
- Caching helps with repeat queries but not with the first query. True cold scan mitigation requires metadata-driven pruning (table formats) and intelligent prefetching.
- Apache Parquet
solvesCold Scan Latency — columnar layout enables predicate pushdown - Lakehouse Architecture, Hybrid S3 + Vector Index
solvesCold Scan Latency — metadata-driven access - Separation of Storage and Compute
constrained_byCold Scan Latency — inherent trade-off - StarRocks
constrained_byCold Scan Latency — first-query limited by S3 access scoped_toS3, Object Storage
Definition
The delay experienced on the first query against S3-stored data, caused by object discovery (listing), metadata fetching, and data transfer over the network.
Connections 29
Outbound 2
scoped_to2Inbound 27
solves24Resources 2
AWS's official S3 performance optimization guide covering request parallelization, prefix design, and throughput targets.
AWS documentation on S3 Intelligent-Tiering, explaining how automatic tier transitions affect retrieval latency for infrequently accessed data.