After 7.5 incredible years, I have resigned from Twitter/X this week. Twitter was always my dream job. Back in college, I was captured by two groundbreaking technologies: Google Wave and Twitter. While it was magical to see real-time updates on my screen from across the globe, Twitter’s profound impact on society truly amazed me. I witnessed passionate discussions on critical issues—conversations so fervent they ignited a spark within me. Even after Twitter’s ban in China, when platforms like 饭否 and Weibo stepped in (though not quite the same), I couldn’t help but feel that magnetic pull. (I even tried joining Weibo once, but that experiment didn’t quite work out!) After graduate school in the U.S., I joined Twitter—the only full-time offer (turned from my internship) I secured at the time. In retrospect, it felt destined. Twitter was not only my first job, but the only company where I’ve ever worked, and every single day was a chance to learn and grow. I’m incredibly grateful for the opportunities I had, the brilliant colleagues from whom I learned so much, and the projects we undertook that made a real impact to the users across the globe. I am especially proud of leading the new Data Engineering team since the acquisition (now the X era). Together, we achieved so much despite limited resources and unseen challenges. I truly believe that X has weathered its toughest times, and the team has some of the most committed and talented engineers ready to drive the company toward rocket growth. I will be cheering them on from the sidelines going forward. Thank you, Twitter/X, for an unforgettable journey that I will forever cherish!

RT @karpathy: New 3h31m video on YouTube: "Deep Dive into LLMs like ChatGPT" This is a general audience deep dive into the Large Language…

Last month I went back to China after almost 14 years in the U.S.. Lives in China have changed so dramatically that I want to share: 1. ID and WeChat are EVERYTHING: The new 3rd generation of Chinese government issued ID has RFID in it which is supported by all major entities for verification purposes, from bank to real estate transactions to all sorts of check-ins and healthcare. With the ID and optionally a backed bank account you can then use WeChat for almost everything in your daily life. It is not just a convenient payment infrastructure like Apple Pay using your phone, it is EVERYTHING -- it is basically Payment + Apple Store + Utilities. WeChat can run other "programs" from 3rd parties. For example, you can order shared rides or make doctor appointment since your identity and payment are integrated with WeChat (more on transportation and healthcare later). Because of its ubiquity, almost all major Apps in China and all merchandise support WeChat -- basically the "mini program" (apps inside WeChat). Nowadays, WeChat and its ecosystem covers vast majority (if not all) retail economics. Oh I forget to mention this, a lower-end smart phone which is more than enough for most people which supports the WeChat ecosystem only costs $100 USD which is unbelievably cheap. 2. Transportation - Subway/CHSR and Electrical Vehicles: My hometown city Xi'an is a 2-tier city in China and my actual hometown is just a "tiny" area of it (though it has the similar population as SF and is known of Terracotta Warriors) yet the city already has 13 metro lines covering most metropolitan area and even some suburb area including my small hometown. The city is even planning for a total of 20 lines down the road. From my hometown which is 25 miles away from one side of the city to the other side of the city which is roughly 45 miles in total would take only 1.5 hours of the subway with 30+ stops. The cost is less than 10 RMB Yuan (~$1.5 USD). For inter-city travels people get used to China High Speed Rail (CHSR). For example, it is 750 miles from Xi'an to Beijing (that's almost doubled distance between SF and LA), lowest tier ticket price is $70 USD which is pretty comfy and spacious but you can also pick up to $200 USD for better tiers. The trip is barely 4.25 hours and it is always on time! I just mentioned one example but there are just so many CHSR lines between major and even smaller cities all over the country which is really hard to imagine for the people in U.S. Because of CHSR, flights are not so crowded but it is also a good alternative which reasonable prices (sometimes lower than CHSR). And then for EV there are just so many choices -- BYD, XPeng, and 10+ other native brands while the imported ones like Tesla (actually natively assembled) and Volkswagen and the like are also very price-attractive. Because of the fierce competition for a typical model (think Tesla's Model 3) the price is ~$30,000 USD across all brands. That is very affordable for mid-class families even without debt (Chinese don't like debt in general) while the experience/quality is promising. One advantage of owning an EV is that, due to the high volume of cars major Chinese cities apply traffic control and on a certain day only some gasoline cars (e.g. plate number ends with odd numbers) can go on the road, but that policy doesn't apply for EVs which means that you can enjoy (maybe) driving whenever you wanted. Because of its prevalence I have more shared EV rides from DiDi (Uber equivalent). For the price of DiDi, 10-15 RMB Yuan (less than $2 USD) any start-end in the downtown area of my small hometown, 20 Yuan ($3 USD) at most for any two points of the entire town. 3. Other Infrastructures: 1) Houses. New buildings (either civil or commercial) are all 20+ story high skyscrapers even in my hometown which you can only see in the downtown area in only some US cities. It is both because there are just so many people and government incentivized the development of real estate in early years (maybe not now in particular). The price was peaked before COVID and now the price is roughly the same level as 2017/2018 before the peak. A 100 square meters house (flat apartment really) costs around $300,000 USD near the tech companies area (Huawei, Tencent etc) in Xi'an. 2) Logistics/Delivery. 2 words: Fast and Cheap. If you live in some southern cities it is same day delivery guaranteed. Even in my hometown it is 3-5 days from everywhere in the country. Food delivery is even more impressive, could be in minutes by many delivery riders on their e-bikes. 3) Malls. Malls are everywhere but most were built before COVID. Nowadays fewer people are shopping in the malls due to the fast development of online shopping, the efficient logistics and delivery mentioned above. Now most people go to malls for good restaurants which are typically at the top level of the building. 4) Highways. Everywhere from Shanghai to Tibet with some are very new and enjoyable to drive. 5) Bridges. My hometown doesn't have a lot water so there is less of them. But in southern cities, fancy and long-distance bridges are built aggressively (e.g. search for Danyang–Kunshan Grand Bridge). 4. Food and Environment. There are just so many choices of different kinds of foods -- restaurants, pick-ups, deliveries. Unfortunately, after almost 15 years staying in the U.S. I am a bit allergic to spicy foods which is the main local flavor. But thank goodness I still loved and enjoyed some of them like 油茶 and 烧饼. There are some discussions about the food quality and safety in China which I can't say much since I didn't stay for so long. During my stay I nonetheless tried to eat more fruits though (peeling is a must!) and they are pretty good and juicy -- citrons, apples, dragon fruit, etc. Alcohol is sold everywhere without clear restriction -- I doubt they check IDs when you buy it. During my reunion with family and friends there are always alcohols and in most cases that was the main theme. I wasn't able to drink much (I barely drink in the U.S.) because the 白酒 (very strong liquor) is too strong and spicy. I am not sure though how the younger generations deal with alcohol, hopefully they are not very interested. Air pollution is still a problem for most northern cities in winter, largely due to the operation of coal mine plants for providing heats. 3 days out of my stay of 10+ days the city is filled with harmful fogs so I had to stay at home. Even for the rest of the days I wear mask most of the time when I am out. As a regular runner, I also didn't run at all during my stay, fearing of potential respiratory damage. The southern part of China is probably better for this matter. There are also much less trails in the city so it is a bit challenging for serious runners/bicyclists. 5. The Healthcare and Insurance. Here I probably need to compare it with what we have in the U.S. since it is hard for people to appreciate it without doing so. After so many years, the healthcare and insurance system in China really astonishes me -- mostly positive with caveats I will explain. China nowadays has way more doctors than the U.S. (>4 million vs. ~1.1 million) while the per capita (3 per 1000) is similar which is already a tremendous achievement. The system also works differently in China: You don't have to make an appointment for a doctor visit and wait for a looong time for specialists -- you can just show up (get up early please) in the hospital or just checkin from WeChat ahead of time and you will be able to see specialized doctors the same day probably less than a couple hours. For surgeries, it can be scheduled within the same month most of the time. For laboratory tests and the medicines there are two sides: On one hand, they are also easy to order and most of them are covered by the insurance, including B-Ultrasounds and CTs (I am not sure even most Americans have ever heard those terms "thanks" to our insurance policy). On the other hand, the doctor visits are mostly test/medicine driven -- making it probably too much for everyone (doctors and hospitals clearly have incentives to order more of those). Another problem of the system is that it still heavily relies on the more advanced equipments and medicines from western world including Japan for the tests and treatments. I've heard that there is also a moderate to heavy usage of traditional Chinese herbal medicine but I can't confirm that. The overall cost of tests, treatments including surgeries is much more affordable comparing to the U.S. and the premium of the insurance is also much lower. For example, a complete set of tests, which include the blood test, B-Ultrasound, CTs of lung and brain, gastrointestinal endoscopy costs about $300 USD in total _before_ insurance. Monthly insurance premium is somewhere between $50 to $100 USD and depending on the policy most people can reimburse 30% to over 90% of the spend. I don't even know how much does it cost of those tests in the U.S. because my doctor never ordered them for me (partially because our insurance company and policy). Other examples: Ambulance for emergency - $50 USD (yes i spelled it correctly), Coronary artery bypass grafting (CABG) surgery (fyi heart disease is no.1 killer in the U.S.) - less than $30,000 USD. Considering it is the life-saving surgery that you may need one day it is just worth it. For surgeries one can probably reimburse at least half of it. How do I know all these? My parents are both retired doctors and I myself did the whole set of tests during my stay (*just worth it*). It makes me remind of Luigi which I definitely don't agree with his action but I do really hope there will be a better insurance system in the U.S. 6. The People and The Culture. Maybe due to my relatively short stay, nowadays people are nicer to each other comparing to 15 years ago -- at least people don't touch your body when you are in waiting lines (was normal which is very irritating). Around 1/3 of the times cars stop and waiting for pedestrians to cross first. I also heard there are much less theft and robbery these days due to the ubiquitous of the phone/WeChat usage and also the mass deployment of camera monitoring system. Because everyone has a smart phone, people are always staring at their phones (similar to U.S.). Douyin (TikTok) and red notes are the most popular ones. The variation of recreations is also flourishing -- people go skiing, climbing mountains (Xi'an is near the most magnificent mountain range of China) and even running more instead of the old-fashioned KTVs. My hometown city also has yearly Marathons (hope I can run it one day) where some of my friends ran once or twice. Smoking in public areas is mostly forbidden, which is a huge improvement. And NO, there is no homeless wandering and randomly threatening people on the street. An interesting observation is that people in China are much more confident nowadays especially when talking with me -- they tend to mention the achievements of the infrastructures as well as the technical advancement (e.g. AI) a lot. A lot people think China is now the firm No.2 country in the world and is not far from U.S. The rest of the world? Not a thing. Overall, there is definitely a tremendous improvement of people's everyday lives and well-beings thanks to the unforeseen speed of the development of infrastructures and the new technologies. Basically as Balaji puts it "China can build (while US can't)" (I don't think U.S. can't build though). The country has become a more livable and enjoyable place for both hardware (infra/tech) and software (people/culture). Most people are super hardworking and pretty positive about the future from what I can tell. I am really glad to see all these and congratulations to them. I also foresee that the competition between US and China will become the main theme in the near future in many major areas. The two countries will lead by a far. I just wishfully hope that this race pushes the limit of homo sapiens without disastrous outcomes.

@richroll I was just listening your podcast with Arthur Brooks last night and saw this post this morning, you inspired so many people including me, pray for you and the affected families 🙏

my (sad) H1B story: After graduating from my PhD program I joined this US company. Starting from 2018 the company had filed a total of 3 times for my H1B (18/19/20), never got selected. Or more precisely I don't even know the result. Every time I asked the HR team they said we need to wait for July to know and there is no email in July. Same store next year. The company also said they filed one in 2017 before I joined but I can't verify that. Some online resources indicate that a Master degree has a 40% chance of being selected, but let's say it is 30%. Being selected for 3 retries is then 76% but yet it didn't happen to me. indicates there are abuses which I am definitely not surprised. During the 3rd lottery, I started my O1 application and that one saved me. Even that got REF and I need to prepare the materials (pretty much highlights of my life and recommendation letters) within the same year. But just found that before getting the green card I'd need to renew my O1 visa every year, which makes it even less appealing than H1B but the effort is much more. During those years we are: 1) family of four, little ones were very young, 2) single-income, 3) living in 1-hour driving to Bay Area (because we can't afford any closer areas), 4) came to US betting the rest of my life (and the whole family) for a better one, 5) had to move apartment twice because our kids are too loud during daytime that annoyed our neighbors -- which we later figured it is just because those are addicted people and apparently their "business" are mainly at nights and they needed precious sleeps during the day. It was really tough and all I can remember is that I've spent a lot time in 2019 preparing my O1 application. I really appreciate the professors and mangers who wrote the recommendation letters for me, they are kind and nice. I never got H1B but this lottery system is just completely broken. I believe it has ended the opportunities of thousands and thousands talented students from all over the world, who would really contribute a lot to this country. I believe eliminating abuse isn't that hard, I believe creating a merit based immigration program isn't that hard, I believe a program without a cap isn't that hard, technically. I hope the discussions can spark a reform of the immigration program so that it is more effective, efficient and fair.

@iuliabaltoi Wish you all the best!

@gennayschweik It is such a pleasure and honor to have worked with you, all the best Genevieve!

@wongmjane Sorry to hear Jane!

wat？

RT @Snowden: If only there were a political movement focused on making the government get out of the way and just leave you alone. An ideol…

@enriquebrgn

Watching the athletes achieve their goals (no matter it is gold, podium or not) is a periodic reminder that persistent hardworking pays off, especially when the goal seems unreachable at the beginning, KEEP ON!

@gennayschweik Congrats 🎊🎉🎈

RT @JoePompliano: Kristen Faulkner (@FaulknerKristen) has one of the craziest stories at this year's Olympics: • Grew up in Alaska • Rowed…

RT @HargunMujral: Just shipped auto-generated captions on @X!

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