SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9313961eae90382718266509154844fb247529d567aabcb8e1c24d682971ae84' 
  AND token = 'MZQWCtZVv0iUiQoF2b4KMWd/nwdhsqOd09LJfoIqYbI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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