- Replace single Redis client with connection pool for better concurrency and auto-reconnection
- Add graceful degradation when Redis is unavailable (None handling in get_users_needing_refresh)
- Add RedisError exception handling with fallback to process all users on mget failures
- Add type hints (Optional[redis.StrictRedis]) to Redis client parameters
- Add health check and socket timeout configuration to connection pool
- Add logging for Redis connection failures and degradation events
- Reorganize imports alphabetically for consistency across both files
- Update get_sync_redis_client to validate connection with ping() before returning
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