WalInsert

This wait event occurs when a process is inserting WAL (Write-Ahead Logging) records into the WAL buffers.

When Does WalInsert Occur?

The WAL insert lock (implemented via WALInsertLock in PostgreSQL source code) is a lightweight lock that serializes access to the WAL buffer.
When a transaction needs to write to WAL (which is every data-modifying operation), following happens:

Acquire the WAL insert lock for its specific insertion slot
Insert the WAL record into the WAL buffer
Release the WAL insert lock

The WALInsert wait event occurs when a backend process is waiting to acquire this lock, indicating contention at one of PostgreSQL's most critical serialization points.

Common Strategies

Stagger batch jobs to avoid concurrent peaks
Increase wal_buffers to accommodate bursts
Use UNLOGGED tables for intermediate results (when safe)
Implement queue-based processing to throttle writes
Remove and Build indexes only after bulk loads are complete
Use COPY FREEZE wherever possible, for initial data load
Increase maintenance_work_mem for index builds
Set synchronous_commit = off temporarily, expecially for bulk loads
Consider pg_bulkload extension for very large imports

Hardware considerations

Use fast storage (NVMe SSDs) for WAL files to reduce write latency, The pg_wal directory should be on fastest storage possible
Ensure sufficient RAM to minimize swapping and improve overall performance
High clock speed and single core performance can help CPU handle high transaction rates efficiently

** Highly recommenedable to test the storage performance using fio or pg_test_fsync to ensure low latency and high IOPS for WAL writes. **