Same-day delivery apparently isn’t fast enough for some Amazon shoppers. The retail giant said on Tuesday it’s adding new shipping options that will get products to front doors within a one- or three-hour window.

The company said in its announcement that the one-hour option is available in hundreds of cities across the US, while the three-hour option is now live in more than 2,000 areas. Amazon’s web page at amazon.com/getitfast shows whether those options are available to shoppers for their location. More than 90,000 products will be available for those shipping windows, the company said.

For those who can’t get those services (including the author of this post, who lives between Austin and San Antonio in Texas), a message will display: “3-hour delivery is currently unavailable. Check back at a later time or shop products with Same-Day delivery below. “

Pricing for the faster delivery options is not cheap: It’ll cost you $20 for one-hour delivery and $15 for three-hour delivery for those without an Amazon Prime account, or $10 and $5 for customers who subscribe to Prime.

Last year, the company rolled out faster Amazon delivery options to 4,000 additional areas. 

In a video of the podcast Learn and Be Curious with Doug Herrington, hosted by Amazon’s CEO of worldwide stores, Kandace Kapps, the director of the company’s same-day strategy team, spoke in more detail about the challenges of fast shipping. Kapps discussed shifts in customer buying habits over the last few years, such as more people buying household essentials like toilet paper on Amazon.

She said that Amazon can deliver so quickly by placing same-day delivery hubs close to customers in metro areas and by getting products ready to ship within 15 minutes, aided by warehouse robots.

“I think customers are going to continue to get magically surprised by how fast we can deliver to their doorstop,” Kapps said. 

Herrington said fast shipping increases sales: “When we speed up the service, the probability that somebody buys a product from us goes up.”

Other retailers, including Walmart, have been adding same-day delivery options or exploring other ways to speed up shipping times to compete with Amazon. 

Removing buyers’ moments of hesitation

Part of Amazon’s strategy, which has involved a massive buildout of locations, deployment of thousands of trucks, deals with other delivery services and investment in logistics software, is actually pretty simple: being there when people need last-minute items or make impulse buys.

“It’s about removing the last moment where you would’ve reconsidered the purchase,” said Stephanie Carls, retail insights expert at coupon and promotional-code website RetailMeNot, a sibling site of CNET. “It changes how you shop, not just how fast you get things.” 

Carls said that Amazon’s super-fast delivery is removing the timeframe when people might change their minds about a purchase.

“There used to be a gap between deciding to buy something and actually having it. That’s when you’d price check, rethink it, or decide you didn’t need it after all,” she said. “This closes that gap.”

The retail expert said that competitors, including Walmart and Target, have been speeding up delivery times in some markets. Still, they’re not matching Amazon’s scale or product range at those speeds or levels of consistency. 

“And that’s what starts to make everyone else feel slow,” Carls said. “Amazon’s advantage is how tightly connected its technology, inventory and delivery networks are, which makes this level of speed more repeatable.”