SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5cf0547fc741ddd924726b372a2f08dd864284e87f3f70981093b44a7f5714f5' 
  AND token = '1lKjtz73IWRiBhlpB9fXd8iEThNJf7daxmUDz2ClvEk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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