Software company AppLovin (APP) will join the S&P 500 Index (SPX) before the market opens on September 22, replacing MarketAxess Holdings (MKTX). APP has been in rally mode since popping 11.5% on Sept. 8, the day of the announcement. The stock was last seen on track for its fourth-straight gain and earlier notched a fresh all-time high of $576.44, with support at the ascending 20-day moving average. The security could also extend its 538.8% year-over-year lead even further, thanks to a historically bullish ...