SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd57801c868fd75c6855a1661bffb7e6b99652c3422553994021dece6bf86c291' 
  AND token = 'leEU29UkBmoAq6eRMtQkEQUt5b6bpkOLh1cXpGtdgFI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}