Datadog (DDOG) - Get Report took off running following its public listing on Thursday, opening at $40.35, about 49% above its IPO price of $27. 

The New York cloud-monitoring-software company estimated its IPO in the $24-to-$26 range, but sold 24 million shares on Wednesday for $27 each ahead of Thursday's public debut. 

Datadog expects to raise about $648 million from its IPO. Datadog is trading on Nasdaq. Thursday's listing values the company at about $7.83 billion.

Cisco Systems (CSCO) - Get Report recently approached Datadog with a takeover offer that would have significantly exceeded the company's post-IPO valuation, according to Bloomberg. The company reportedly rebuffed that offer.

Datadog shares are trading up 37% at $37.04.