New Delhi, July 30 -- TEMPE, Ariz. - Three years ago, Carvana Co. was in negotiations with its creditors about the terms of its debt. On Wednesday, the Tempe-based online used-car marketplace announced the best quarter in company history. By the time after-hours trading closed, the stock had fallen 15 percent.

The tension in that sequence captures what investors found when they looked past the headline.

The figures for the three months ended June 30 were genuine records across every metric the company publicly tracks. Total revenue reached $7.38 billion, up 52 percent year over year. Net income came in at $513 million, against $308 million in the comparable period last year. Retail unit sales rose 38 percent to 197,325 vehicles, the ten...