Concurrent workloads in MySQL Shell are not thread safe.
Very difficult yo simulate and diagnose.
Look for:
- metadata locks
- lock timeouts
- deadlocks
Schema knowledge can misloead during diagnosis. Look at actual locks.
Note Foreign keys are a bigger issue with metadata locks than for InnoDB record locks as the latter only affect cases where the columns used in foreign keys are involved.
With FK, set lock_wait_timeout low; also reduce max_write_lock_count.
May have to remove FK in some cases.
Handle errors as they happen to clean up resources quickly.