SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '471bc88b51f47150ae820d7f5b645a368bb247eb54cd14626020efdc54c620a2' 
  AND token = '/b+GHVwGELkPVDqxtU91f/pUI/yqahVUhyYYXBGuvhw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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