Instacart, the grocery delivery startup, has raised an additional $150 million in funding. This new cash is part of its existing Series E round and in addition to the $200 million the company raised in February. Axios broke the story this morning with the company later confirming it.

This new money brings the total amount raised by Instacart to more than a billion dollars. According to Bloomberg, the additional funding raises the company’s valuation to $4.35 billion.

Instacart is going to need all the money it can get as it works to fend off Amazon, which started rolling out two-hour deliveries from its subsidiary Whole Foods earlier this year. Instacart actually has its own delivery partnership with Whole Foods, but obviously with Amazon’s latest moves, that deal is not long for this world.

To make up for this expected loss, Instacart has been busy signing up additional retailers like Costco, Kroger, Albertsons and Sam’s Club. That last one is of particular interest as Walmart owns Sam’s Club. Walmart shut down 63 Sam’s Clubs in January, but if the Instacart partnership bears fruit, it could lead to bigger opportunities for for both companies as they look to keep Amazon at bay.

Having a variety of large partners is good for Instacart, but it will have to battle Amazon on the technology front as well. Just today, Amazon announced expanded smart lock compatibility for its Key service in a bid to bolster its in-home delivery capabilities. Whether or not people will ever be comfortable with letting strangers into their unattended home is TBD, but the point is that Instacart will need to use this money to both expand and innovate.