SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6cc18a97fa17ccf2bb525ee1222ff35e0aa09c630400c16efd139017efd5d8bb' 
  AND token = '4sUlZEuihe7aghpcWZEFyCxk+l717DrIPu958K2Mo3E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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