Amazon.com Inc.’s pledge last month to pump $800 million into making next-day delivery the new standard upped the pressure on its brick-and-mortar rivals to spend more trying to catch up all over again.

That’s good news for logistics startups helping Walmart Inc., Best Buy Co., Macy’s Inc. and other retailers compete online. These upstarts, often led by Amazon alumni, say their phones are ringing with new inquiries and that venture capitalists are keen to pony up.

Seattle startup Flexe, which operates a marketplace for warehouse space and online order fulfillment, today announced a $43 million investment led by New York firm Tiger Global. Dolly, another Seattle startup, recently announced $7.5 million in fresh funding to expand to new cities and start delivering televisions, sofas, appliances and other big items for the likes of Lowe’s Cos. and Costco Wholesale Corp. Dolly was originally a marketplace for movers.

Retailers that struggled to match Amazon on two-day deliveries have to spend big yet again to further cut delivery times. Amazon will capture almost half of the $600 billion U.S. shoppers will spend online this year, according to EMarketer Inc., and retailers have to match its delivery speed to keep that dominance from growing.

“Interest in logistics investments has picked up, and we’ll see even more of that this year,” says Julian Counihan, a partner at Schematic Ventures in New York. “Retailers traditionally invested in physical stores to increase sales. Amazon flipped that on its head and made logistics the driver of customer experience.”

Flexe, which counts Walmart among its customers, aims to double in size to more than 160 people this year to keep up with demand. It hired former Amazon transportation vice president David Glick as chief technology officer to expand its e-commerce fulfillment business, which now accounts for three-fourths of all sales.

Flexe rents out space and services in more than 1,000 warehouses, providing an alternative to Amazon’s logistics services. Flexe helps warehouse owners and operators utilize empty space and idle workers by connecting them with retailers requiring flexibility to manage seasonal demand. Ace Hardware, for instance, used an organic tomato farm’s warehouse in the winter to stockpile imports since weather delayed the usual start of the spring home improvement season.

“Having big customers like Walmart known for high standards brings legitimacy to our business,” Flexe CEO Karl Siebrecht says.

Dolly’s focus on delivering big, bulky items is something Amazon is still trying to figure out. Amazon retail CEO Jeff Wilke, whose job includes challenging Wayfair Inc. in online furniture sales, boosted his own personal investment in Dolly in the latest round, which was led by Unlock Venture Partners. Dolly offers furniture moving and delivery services in 11 U.S. cities, including San Francisco, Los Angeles and Chicago.

The company connects retailers and customers with 10,000 independent contractors who move and deliver the items. Dolly plans to use the funding round to expand to some 30 markets within the next 12 months to meet demand. Deliveries of sofas, televisions and appliances can be done is as little as 90 minutes, the company says.

“We give retailers the ability to tell their customers that they offer way better terms than Amazon for big and bulky items,” says CEO Mike Howell. “Amazon wants to sell more furniture, but it’s having a very difficult time meeting its customers’ expectations because delivering furniture is so much different than delivering small parcels.”

Logistics software firm Milezero, which has Staples Inc. as a customer, has also experienced an uptick in business since Amazon’s next-day delivery pledge, says co-founder Charles Griffin. Retailers are starting to realize that employing humans to trawl the aisles filling online orders isn’t efficient and are investing in software that essentially turns stores into warehouses.

“Retailers realize these personal shopper solutions are just a band-aid,” says Griffin, a former Amazon vice president.

The interest will only keep heating up as the busy holiday season approaches and retailers look for ways to keep Amazon from gobbling up more sales. Last-minute shoppers are one of the last places retailers have an edge over Amazon, and next-day delivery blunts that advantage.

“Jeff Bezos is absolutely our best salesman,” says Daphne Carmeli, CEO of Deliv, which provides delivery services for retailers like Macy’s in 35 metro markets and announced a $40 million investment last summer. “He comes out with something and our phones light up.”