Former ByteDance employee's account: How I started with two Pinduoduo hard drives and made six times the profit with Seagate to achieve financial freedom?

Author: Leto Bao, the protagonist of achieving financial freedom with 30 million in ByteDance stock trading

All the information below was shared in the ByteDance US stock group last year, including trading targets and position gains and losses, all of which can be verified.

Last August, I originally just wanted to buy two hard drives.

At that time, I was setting up a small quantitative platform and wanted to pull some tick-level market data to store locally. I needed a place to store dozens of terabytes of data, so I ordered two large-capacity Seagate drives on Pinduoduo. Looking back, this hard drive was the starting point for my storage investments over the past two years.

Hard Drive Prices Started to Change Daily

After receiving the hard drives, I saved the link, planning to buy more if needed. A few days later, I checked again, and the price had increased; a few days later, it rose again. The same model, from the same store, had its price adjusted several times within a week, and it was only going up.

For an industrial product with high production capacity and standardization, the retail price should not continuously rise in one direction like this. I considered it a noteworthy anomaly rather than just a simple price increase by the seller.

I used price comparison tools like Shuaima and Keepa to pull the price curve of this hard drive over the past few months and compared it with several other large-capacity models from Seagate and Western Digital. The conclusion was consistent: it wasn't just a single model issue; the entire product line of large-capacity mechanical drives was rising, and it was a sustained, one-way increase, unlike short-term fluctuations caused by promotions.

At this point, it was basically confirmed that there was a larger reason behind it.

Following This Lead, AI is Competing for Hard Drives

As I dug deeper, the logic gradually became clear.

The market is more focused on AI's demand for graphics cards, but its demand for storage is equally huge. Training and inference of large models generate massive amounts of data that need to be stored long-term, and for long-term, low-cost data storage, it mainly relies on large-capacity mechanical hard drives, not SSDs. The type of drives used in data centers is called nearline enterprise hard drives, which large cloud providers like Microsoft, Amazon, Google, and Meta are purchasing in large quantities.

Seagate happens to be in the midst of this demand wave. Its promoted HAMR technology can significantly increase single-drive capacity, which aligns perfectly with the needs of data centers. With limited production capacity, manufacturers prioritize supplying higher-margin enterprise orders, thus squeezing the supply on the retail side. The price increase I saw on Pinduoduo essentially reflected the procurement demand from AI data centers, which was transmitted to consumer prices.

I checked Seagate's financial report at that time: revenue for the most recent quarter increased by 39% year-over-year, and the gross margin set a record. The market also began to price the data storage sector as a part of the AI industry chain.

After confirming the logic, I bought 500 shares at over $150 and shared my reasons for buying, costs, and position in the company's internal US stock chat group.

What Made Me Confident to Increase My Position Was the Subsequent 13F

Thinking it through myself wasn't enough; I needed to confirm whether institutional funds were making the same judgment.

In the US stock market, there is a very useful piece of public data: institutions managing over $100 million must disclose their US stock holdings every quarter, known as 13F. This is equivalent to a legal, public record of institutional holdings that anyone can access.

I didn't immediately increase my position but wanted to observe the trend for another quarter or two. Changes in a single quarter might be coincidental, while consistent trends over several quarters are more credible. By the time the November issue, which was the third quarter's 13F, came out, connecting Seagate's institutional holdings over the past year formed a clear direction:

In the second half of 2024, this stock was basically ignored, with the number of institutions holding it remaining at over 800, even slightly decreasing. Entering the second quarter of 2025, there was a clear turnaround, and in the third quarter, it accelerated further: the number of institutions holding it increased from over 800 to over 1,200, and the number of new institutions entering each quarter was also rising.

It should be noted that the market value of holdings rose to $45.6 billion within a year, a significant portion of which came from the increase in stock price itself, not solely from new funds. However, indicators like the number of institutions and the number of new positions, which reflect "breadth," are more telling; their quarterly increases indicate that this is not just a bet by one or two funds, but a continuous entry of a group of professional funds.

Once I confirmed this, I felt more confident to significantly increase my position and began to seriously study the storage sector, subsequently also starting to accumulate $STX and $SNDK through LEAPS CALL options.

Looking Back Now

On the day I bought the hard drives, Seagate closed at over $150; today it is just over $965, having increased more than sixfold, and at one point last year, it surpassed Palantir to become the S&P 500's top performer for the year. Just from those initial 500 shares, the unrealized profit is around $400,000, and I won't detail the subsequent accumulation.

The two hard drives ultimately led to such a transaction, which still feels somewhat unexpected.

Summarizing This Thought Process

It's actually not complicated:

• Anomalies in everyday items (price increases, shortages, queues) often appear earlier than news and financial reports. Sometimes, ordinary people receive firsthand signals earlier than professional institutions.

• Don't stop at the impression of "it seems to have become more expensive." Pulling the price into a curve can help determine whether it's a trend or noise.

• Further inquire: Is there a long-term, structural demand behind this? Then find publicly listed companies that can directly benefit and are in key positions in the industry chain.

• Finally, use 13F to verify institutional attitudes and observe trends over several consecutive quarters, rather than just a single quarter.

This method does not guarantee correctness every time, but at least it allows purchases to be based on logic rather than gut feeling.

Finally, Clarifying the Risks

This was a successful instance. I have also had experiences where I focused on a price increase signal that ultimately proved to be just a short-term fluctuation; those were not shared in the group but were equally real, and survivor bias is quite evident.

The above is a personal review and does not constitute investment advice; profits and losses are at your own risk.

However, I endorse this thought process: pay attention to anomalies in everyday encounters, ask one more layer of reasons, find the underlying publicly listed companies, and then check if professional funds agree using 13F. The next time something you frequently buy inexplicably increases in price, you can think about: who is profiting from this money, and whether that company is already publicly listed.

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