SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '840fec102188195a00cbfed84db03291da8efea8c205d67bc958cb52a295cdea' 
  AND token = '8+AmVOdMmbwGGDYtAJLfryfy9Ek/7T7PQdiph9aiu60=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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