What: Shares of cloud security company Qualys (QLYS 0.98%) jumped on Tuesday after the company reported its second-quarter results, matching analyst estimates for revenue and beating estimates for earnings. The stock was up as much as 18% early in the day and by 1:50 p.m. was up 4.6% from the previous close.

So what: Qualys reported quarterly revenue of $39.9 million, up 23% year-over-year and in-line with analyst estimates. The company pointed to both subscription sales to new customers and upsells to existing customers as the drivers behind this revenue growth.

The company reported non-GAAP EPS of $0.16, up from $0.11 during the same period last year and five cents higher than analyst estimates. Qualys' deferred revenue balance rose by 22% year-over-year, leading to $15 million of free cash flow for the first half of the year, a near-doubling compared to the first half of 2014.

Qualys' guidance for the third quarter was mostly in line with analyst estimates. The company expects revenue between $42 million and $42.5 million and non-GAAP EPS between $0.12 and $0.14. Analysts were expecting revenue and EPS of $42.8 million and $0.13, respectively.

Now what: While Qualys' results were solid, it's hard to justify this big of a jump. Shares are still well below peak levels from earlier this year, and following a sell-off back in May driven by weak guidance from the company, expectations were likely low.

Qualys is an extremely expensive stock, trading at around 10 times last year's sales, a valuation that its growth rate doesn't really justify. While investors are cheering Qualys' solid quarter by sending the shares higher, the stock's high price makes it a risky bet.