SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dfdc7c949f331c392bbc8bbd34417bb31c1b440fc7b6dd2999949e674fbd3f7b' 
  AND token = 'E36DoNTE9QoZBVqlJUIpCfydujaJafj53aEysbuUYDk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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