Overhead of pg_stat_statements and pg_stat_kcache

Nikolay and Michael discuss the overhead of pg_stat_statements and pg_stat_kcache — mostly focusing on some interesting things Nikolay found while stress-testing some large spot instances up to and beyond 2m TPS(!) 
 
Here are some links to things they mentioned:

• pg_stat_statements https://www.postgresql.org/docs/current/pgstatstatements.html
• pg_stat_kcache https://github.com/powa-team/pg_stat_kcache
• pg_stat_statements overhead estimate in pganalyze FAQs https://pganalyze.com/faq
• What is the performance impact of pg_stat_statements? (DBA Stack Exchange answer with several links) https://dba.stackexchange.com/questions/303503/what-is-the-performance-impact-of-pg-stat-statements
• Towards Millions TPS (blog post by Alexander Korotkov) https://akorotkov.github.io/blog/2016/05/09/scalability-towards-millions-tps
• Postgres.ai blog post with links to …

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