SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '87a202c3d7a448e9157dee8937c68c6a2b30e5f657f0436abad25477be86d241' 
  AND token = '8JjtWyNPSDEGGbC89UjgF8gjrnNIfC+DqIDkvWD51aM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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