SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '64376d9ae6c42af42652e890fc72d30e841c54608b8adb5a87708470ece4b1a8' 
  AND token = 'UJV95cgJwrQcxb2GhFljwnut9XLvWFxhI7rtJV/9kug=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}