SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe6a298b15f4c1e687297e9b04db722a942f2dbe829fceba47b8437baaaf3000' 
  AND token = 'CxlGT3oCuwhi5KEzFwbn+NWmYvp/WbgmRMJtTWRPos0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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