Amazon.com Inc. has escalated its assault on the grocery delivery market by expanding same-day shipping to include perishable items like milk, meats and frozen foods, a move that sent shockwaves through competitors’ stock prices on Wednesday. The e-commerce giant announced it would roll out this service to more than 3,300 U.S. cities and towns by year’s end, allowing Prime members to bundle groceries with other purchases for rapid delivery. Shares of Instacart parent Maplebear Inc. plunged over 10%, while DoorDash Inc. and supermarket chains like Kroger Co. each dropped around 4%, according to data from Investing.com.

This expansion builds on Amazon’s June commitment to invest $4 billion in faster delivery infrastructure, targeting rural areas and aiming to cover 4,000 communities. Doug Herrington, CEO of Worldwide Amazon Stores, emphasized the convenience, noting customers can now “order milk alongside electronics and have everything delivered within hours,” as quoted in a company press release. The initiative directly challenges services like Instacart and Walmart+, which have dominated quick grocery fulfillment.

Market Ripples and Investor Reactions

The immediate market fallout underscores investor fears of Amazon’s growing dominance in a sector projected to reach $1.2 trillion globally by 2030. Walmart Inc. shares dipped 2%, and Uber Technologies Inc., parent of Uber Eats, fell 1%, reflecting broader concerns about intensified competition. Analysts at Zerohedge described the launch as a “direct hit” on home delivery specialists, pointing to Amazon’s vast logistics network as a key advantage.

Meanwhile, supermarket operators like Albertsons Cos. and Target Corp. also felt the pressure, with stocks declining amid worries that online convenience could erode in-store traffic. Posts on X (formerly Twitter) captured the sentiment, with users highlighting how Amazon’s move amplifies existing trends where consumers prefer home delivery over physical shopping, even at a premium cost, echoing patterns seen during the pandemic.

Historical Context and Strategic Shifts

Amazon’s push into groceries isn’t new; it acquired Whole Foods in 2017 for $13.7 billion, but initial forays into delivery lagged behind rivals. Instacart, valued at $39 billion in recent funding rounds, built its empire on partnerships with chains like Kroger and Costco, boasting growth of over 400% in online sales during early COVID-19 surges, per reports from Reuters. DoorDash, meanwhile, expanded from meals to groceries, integrating with platforms like Albertsons.

Yet, Amazon’s latest strategy leverages its Prime ecosystem—over 200 million subscribers worldwide—to undercut competitors on speed and integration. Unlike Instacart’s model, which relies on gig workers and markups, Amazon promises free delivery on orders over $25 for Prime members, potentially squeezing margins for others. Walmart, with its $98 annual Walmart+ membership offering sub-three-hour deliveries, has seen success, but Amazon’s scale could force price wars.

Competitive Responses and Future Implications

Rivals are scrambling. Instacart has invested in automation and partnerships, but its stock tumble suggests vulnerability; analysts from Yahoo Finance note that Amazon’s entry could capture 20% more market share in urban areas. DoorDash, fresh off acquisitions, may pivot to niche services like alcohol delivery to differentiate.

Looking ahead, this could reshape retail dynamics, pushing supermarkets toward hybrid models. Kroger’s digital sales grew 8% last quarter, but Amazon’s aggression might accelerate consolidations or tech investments. Industry insiders warn of a “delivery arms race,” where only giants with deep pockets survive, potentially benefiting consumers with lower costs but challenging smaller players. As one X post from a financial analyst put it, “Amazon’s grocery play is the quick-commerce killer we’ve been waiting for.” With economic uncertainties, the true test will be sustaining growth amid inflation and shifting consumer habits.