JD.com Inc. added so much warehouse space in three months that the new construction could cover just about every inch of Monaco, a pace of expansion that rivals growth at Amazon.com Inc.

China’s second-largest e-commerce service added 2 million square meters (21.5 million square feet) of warehouse space from July to September, about equal to the span of the city-state famed as a getaway for the rich. It ran 405 warehouses encompassing 9 million square meters at the end of September — adding about a warehouse every one to two days. December-quarter data won’t be available till JD reports results, which aren’t expected till at least next month.

JD builds and runs its own nationwide logistics chain, a costly approach that’s weighing on profitability but that it believes is crucial to competing against larger arch-foe Alibaba Group Holding Ltd.