## TL;DR
The Query Acceleration Service (QAS) offloads parts of eligible queries to extra serverless compute, speeding up large scans without resizing your warehouse. Enable it per warehouse, cap the max scale factor, and let Snowflake decide per query. It helps most with full-table scans and heavy aggregations on big tables; it does nothing for queries that are already fast or bottlenecked on something else.

## The query
```text
snowflake query acceleration service explained
```

## Use this when
- Large analytical queries scan slowly even though the warehouse looks idle
- You want faster scans without permanently upsizing the warehouse
- Queries do heavy filtering, aggregation, or joins over big tables

## Not for
- Small queries or dashboards that already return in seconds
- Point lookups and OLTP-style patterns
- Replacing proper clustering keys or query rewrites

## Steps

1. Confirm the query is actually eligible. QAS accelerates table scans, filters, projections, and aggregations on large tables. Check the query profile: if most time is in table scan, QAS can help. If time is in external functions or queueing, it will not.

Expected output: a query profile showing scan as the dominant cost, which marks the query as a QAS candidate.

2. Enable it on the warehouse with a scale factor cap:

```sql
ALTER WAREHOUSE analytics_wh SET QUERY_ACCELERATION_MAX_SCALE_FACTOR = 8;
```

Expected output: the warehouse property is set; nothing changes until an eligible query runs.

3. Run the slow query and compare. Snowflake decides per query whether acceleration applies; check QUERY_HISTORY or the profile for acceleration usage and elapsed time before and after.

Expected output: measurably lower elapsed time on the target queries, with acceleration noted in the profile.

4. Watch the cost. QAS bills serverless compute credits per second of accelerated work. Monitor usage in the account usage views and lower the scale factor if the bill grows faster than the speedup is worth.

Expected output: a weekly cost trend for accelerated compute that stays proportional to the performance gain.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_LDpBd3-Vv-H56RFGD5uVOg