Germany-based apparel and shoe web retailer Zalando says more efficient fulfillment, better marketing and strong sales leading into the spring and summer helped it achieve a strong first quarter.

The retailer says its Q1 2014 sales rose 35% year over year to reach $689.48 million compared to $511.95 million in Q1 2013. Sales in Zalando’s core markets of Germany, Austria and Switzerland totaled $390.84 million, up 27% from $306.89 million in Q1 2013.

“The start to the year has been promising, with a significant improvement in Q1 margin year-on-year, so we are on track with our plans for 2014,” says Rubin Ritter, a member of the Zalando management board.

During the quarter the retailer completed its expansion  of its fulfillment center in Erfurt, Germany. This extension helped the retailer improve fulfillment efficiency, the retailer says. It also is ramping up operations at its new fulfillment center in Mönchengladbach, Germany. 

Zalando says it booked 332 million total visits to its sites in the first quarter of 2014, compared to 275 million a year earlier. Additionally, 38% of traffic to Zalando e-commerce sites stemmed from mobile devices (including both smartphones and tablets) during the quarter. Zalando says it plans to launch localized apps for several countries over the summer.

At the end of the quarter Zalando had 13.5 million active customers compared with 10.3 million at the end of Q1 2013. The retailer also rolled out more pick-up points in Q1 enabling online shoppers to retrieve goods nearby rather than have them delivered to their homes.  

Zalando, which is based in Berlin, sells more than 150,000 products from 1,500 brands.