SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2471eb1393853de3236a8eb7e9667059d56fef57d9b7b51f9a2950ff73aa54b2' 
  AND token = '4pL4gQkphHZdFuWZp4BwPMY6jVj5Zc9m56Y07sSC8Ok=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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