KEY POINTS
  • Amazon reported fourth-quarter results on Thursday that smashed analysts' expectations. 
  • The company's profits rebounded during the quarter, while revenue climbed 21% year over year. 
  • The outperforming results show Amazon's big investments in one-day delivery are paying off.

Shares of Amazon climbed as much as 11% in extended trading on Thursday after smashing earnings expectations for the fourth quarter.

The company's market cap surged above $1 trillion after hours on the back of the powerhouse earnings report. In doing so, it joined Apple, Alphabet and Microsoft, which have all crossed the trillion-dollar threshold. Amazon first reached a $1 trillion market cap in September 2018.