When tuning PostgreSQL, what did you rely on when changing configuration parameters?

When tuning PostgreSQL, I relied on several key factors:

• Load analysis and profiling: studied which queries are most frequent and resource-intensive, used EXPLAIN ANALYZE to evaluate execution plans.
• Metrics monitoring: looked at CPU, memory, disk usage, lock counts, and wait times.
• Memory parameters: configured shared_buffers (usually 25-40% of RAM), work_mem for sorts and hashes, effective_cache_size for OS caching estimates.
• Parallelism settings: max_parallel_workers_per_gather, parallel_tuple_cost, and others to optimize parallel queries.
• WAL and checkpoint tuning: parameters like wal_buffers, checkpoint_timeout, checkpoint_completion_target to balance performance and reliability.
• Automatic tuning and recommendations: used tools like pgTune and log-based suggestions.

Ultimately, changes were based on specific metrics and system behavior under load, rather than guesses.