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docs/source/configuration/in-memory-caching.mdx

@@ -82,6 +82,11 @@ then look at `apollo_router_schema_loading_time` and `apollo_router_query_planni
 #### Cache warm-up with distributed caching
 
 If the Router is using distributed caching for query plans, the warm-up phase will also store the new query plans in Redis. Since all Router instances might have the same distributions of queries in their in-memory cache, the list of queries is shuffled before warm-up, so each Router instance can plan queries in a different order and share their results through the cache.
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+#### Schema aware query hashing
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+The query plan cache key uses a hashing algorithm specifically designed for GraphQL queries, using the schema. If a schema update does not affect a query (example: a field was added), then the query hash will stay the same. The query plan cache uses that key during warm up to check if a cached entry can be reused instead of planning it again.
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 ## Caching automatic persisted queries (APQ)
 
 [Automatic Persisted Queries (**APQ**)](/apollo-server/performance/apq/) enable GraphQL clients to send a server the _hash_ of their query string, _instead of_ sending the query string itself. When query strings are very large, this can significantly reduce network usage.