SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dfd4b1be13db294202907536ebf636467f4e5a23b5fa2bd6f30490bd6ef63764' 
  AND token = '39B4mHskicZZGLrzlWh0jWucvRTasw8qpZDPJevQBuc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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