Two changes combined:
1. historical-query-slow-connection: Migrate all historical query pages
to read_sql_df_slow with semaphore concurrency control (max 3),
raise DB slow timeout to 300s, gunicorn timeout to 360s, and
unify frontend timeouts to 360s for all historical pages.
2. hold-resource-history-dataset-cache: Convert hold-history and
resource-history from multi-query to single-query + dataset cache
pattern (L1 ProcessLevelCache + L2 Redis parquet/base64, TTL=900s).
Replace old GET endpoints with POST /query + GET /view two-phase
API. Frontend auto-retries on 410 cache_expired.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
71c8102de6