--- title: 2025 Year in Review link: https://eugeneyan.com//writing/2025-review/ source: eugeneyan-com published: 2025-12-14T00:00:00Z updated: 2025-12-14T00:00:00Z first_seen: 2026-09-27T19:29:15.293681927Z labels: - life summary: An eventful year of progress in health and career, while making time for travel and reflection. content: extracted html: 2025-12-14-2025-year-in-review.html preview: file: 2025-12-14-2025-year-in-review.preview-71ba533b635c.webp width: 256 height: 134 color: '#425b66' images: - source: https://eugeneyan.com/assets/og_image/2025-review.jpg original: file: 2025-12-14-2025-year-in-review.image-e4304553c3c4.jpg width: 1200 height: 630 color: '#040406' - source: https://eugeneyan.com/assets/heartrate.webp original: file: 2025-12-14-2025-year-in-review.image-73db77824e97.webp width: 1200 height: 418 variants: - file: 2025-12-14-2025-year-in-review.image-b64d4a0aef9c.webp width: 320 height: 111 color: '#fdfdfd' - source: https://eugeneyan.com/assets/vo2-max.webp original: file: 2025-12-14-2025-year-in-review.image-6ca965909c0a.webp width: 1200 height: 490 color: '#fdfcfc' - source: https://eugeneyan.com/assets/2025-top20.webp original: file: 2025-12-14-2025-year-in-review.image-fac9245c79ef.webp width: 961 height: 1111 variants: - file: 2025-12-14-2025-year-in-review.image-7bc9b1d74cef.webp width: 320 height: 370 color: '#f9fafa' - source: https://eugeneyan.com/assets/2025-search.webp original: file: 2025-12-14-2025-year-in-review.image-e21124d5d04d.webp width: 1200 height: 547 variants: - file: 2025-12-14-2025-year-in-review.image-7d76ea6406a0.webp width: 320 height: 146 color: '#fcfcfc' - source: https://eugeneyan.com/assets/icon-twitter.svg original: file: 2025-12-14-2025-year-in-review.image-9f73746a86e9.png width: 512 height: 512 variants: - file: 2025-12-14-2025-year-in-review.image-10d32c0d6dac.webp width: 320 height: 320 - file: 2025-12-14-2025-year-in-review.image-1a1653690e12.webp width: 512 height: 512 color: '#000000' - source: https://eugeneyan.com/assets/icon-linkedin.svg original: file: 2025-12-14-2025-year-in-review.image-50dfb45d5f9e.png width: 505 height: 505 variants: - file: 2025-12-14-2025-year-in-review.image-b7fdeee63d68.webp width: 320 height: 320 - file: 2025-12-14-2025-year-in-review.image-003cf9435e7e.webp width: 505 height: 505 color: '#000000' - source: https://eugeneyan.com/assets/bluesky.svg original: file: 2025-12-14-2025-year-in-review.image-cd93481613cb.png width: 600 height: 530 variants: - file: 2025-12-14-2025-year-in-review.image-1790c4125e73.webp width: 600 height: 530 color: '#1084fd' - source: https://eugeneyan.com/assets/icon-facebook.svg original: file: 2025-12-14-2025-year-in-review.image-68df389f82c9.png width: 256 height: 256 variants: - file: 2025-12-14-2025-year-in-review.image-6035d4122baf.webp width: 256 height: 256 color: '#3b5998' - source: https://eugeneyan.com/assets/icon-mail.svg original: file: 2025-12-14-2025-year-in-review.image-bf2110bd7265.png width: 512 height: 512 variants: - file: 2025-12-14-2025-year-in-review.image-c80acd329b85.webp width: 320 height: 320 - file: 2025-12-14-2025-year-in-review.image-84c4e78a876d.webp width: 512 height: 512 color: '#000000' - source: https://i.ytimg.com/vi/qNmxL_XCfoU/hqdefault.jpg original: file: 2025-12-14-2025-year-in-review.image-06c52237a9c7.jpg width: 480 height: 360 color: '#383838' --- 2025 was an eventful year of progress. I doubled down on my health, had some pleasant career surprises, and my wife and I made time for two vacations. > Past years: [2024](https://eugeneyan.com/writing/2024-review/), [2023](https://eugeneyan.com/writing/2023-review/), [2022](https://eugeneyan.com/writing/2022-in-review/), [2021](https://eugeneyan.com/writing/2021-year-in-review/), [2020](https://eugeneyan.com/writing/retrospective-2020/) ## Reviewing my 2025 Goals **✅ Write 6 substantive pieces**: Before 2023, most of my technical writing focused on RecSys. In 2023 - 2024, this shifted towards applying LLMs. In 2025, I worked to bridge these two interests, starting with a deep dive on [*Improving RecSys & Search in the Age of LLMs*](https://eugeneyan.com/writing/recsys-llm/), and then following up with a walkthrough on finetuning an [*LLM-RecSys Hybrid for Steerable Recs with Semantic IDs*](https://eugeneyan.com/writing/semantic-ids/). The deep dive was well received and led to an invitation from the AI Engineer World’s Fair to host the [first-ever LLM × RecSys track](https://x.com/swyx/status/1979291014990074030). The other major themes for 2025 were [evals](https://eugeneyan.com/tag/eval/)—an area where we still have much to learn and do as an industry—as well as general leadership and writing advice. Here are the six pieces: - [Improving Recommendation Systems & Search in the Age of LLMs](https://eugeneyan.com/writing/recsys-llm/) - [Training an LLM-RecSys Hybrid for Steerable Recs with Semantic IDs](https://eugeneyan.com/writing/semantic-ids/) - [Evaluating Long-Context Question & Answer Systems](https://eugeneyan.com/writing/qa-evals/) - [Product Evals in Three Simple Steps](https://eugeneyan.com/writing/product-evals/) - [Advice for New Principal Tech ICs (i.e., Notes to Myself)](https://eugeneyan.com/writing/principal/) - [Frequently Asked Questions about My Writing Process](https://eugeneyan.com/writing/writing-faq/) **✅ Prototype 4 apps**: One of my all-time favorites is [AI Reading Club](https://aireadingclub.com) (ARC; [how it’s built](https://eugeneyan.com/writing/aireadingclub/)). Inspired by [Karpathy’s tweet](https://x.com/karpathy/status/1866896395363553418), I built ARC to help people get more out of reading. I wasn’t satisfied with existing workarounds, like [uploading PDFs to a chatbot](https://x.com/patrickc/status/1866899075901296752), because I thought they distracted from the experience of reading the book. Building ARC gave me an opportunity to design my ideal reading experience. And now, it’s [available on the Kindle iOS app](https://www.aboutamazon.com/news/books-and-authors/kindle-recaps-feature-ebook-series-refreshers)! Another favorite was training an [LLM-RecSys Hybrid for Steerable Recommendations with Semantic IDs](https://eugeneyan.com/writing/semantic-ids/). The goal was to combine the world knowledge of LLMs with the behavioral-based, next-event prediction of RecSys. I started with the expectation that it would *not* work, and was shocked when the model could natively recommend items based on natural language and/or item ID input. I still recall the “mind-blown” moment while watching the model being trained: Given an input Zelda game (on Nintendo) and a request to filter for similar games on Xbox, it was able to recommend three action-adventures—the same genre as Zelda—on Xbox. Other smaller prototypes include [building sub-agent capabilities into q-cli](https://eugeneyan.com/writing/news-agents/) (before they were available anywhere) and a [stock analysis app](https://x.com/eugeneyan/status/1927217797458719061) for my family. **✅ Health**: I started running 5km weekly since July. While I had tried to do this previously, I was never consistent. Sticking to it led to noticeable improvements in my resting heart rate and VO2 max, as measured by my Apple Watch. Looking at the data from 2023 - 2025, I can see small but gradual improvements, and I aim to continue making progress on next year. ![Image](https://eugeneyan.com/assets/heartrate.webp "Image") Resting heart rate from 2023 - 2025 ![Image](https://eugeneyan.com/assets/vo2-max.webp "Image") V02 max from 2023 - 2025 **❌ Snowboarding (do a black run in 2026)**: This goal fell short as I’ll have to skip the current season due to surgery. Nonetheless, my wife and I are happy with the progress we made earlier in the year (in Hakuba) and are eager to hit the slopes next season. [YouTube video player](https://www.youtube.com/watch?v=qNmxL_XCfoU) ## Health: Braces and jaw surgery To fix my bite and prevent prematurely grinding down my molars, I started wearing braces in February and had jaw surgery in late November. I adapted to the braces more easily than expected, and am now in my third week of recovery from the surgery. I got promoted to Principal Applied Scientist and have been enjoying the officially increased scope and learning that comes with it. I wrote [this](https://eugeneyan.com/writing/principal/) to share what I’ve learned so far from role models and mentors. Separately, my O1 visa was approved. ## Travel: Hakuba and Las Vegas My wife and I aim to travel at least once a year, ideally twice if possible. Our two trips this year were to Hakuba (a snow resort town, lesser-known than Niseko) and my first-ever trip to Las Vegas. The snowboarding and food in Hakuba were the best I’ve experienced, and I now have a new life goal to visit at least once a year, time and budget permitting. For Vegas, my top recommendations are Antelope Canyon, watching a show at The Sphere, and the Bellagio fountains (imagine the mechanical engineering involved in 1998!) ## Site statistics for 2025 Here are the top 20 most interacted-with pieces on my site. ![Image](https://eugeneyan.com/assets/2025-top20.webp "Image") Top 20 most interacted-with pieces in 2025 And here are the Google search metrics. While impressions increased from 1.97M to 3.39M (+71% YOY), clicks decreased from 56.5k to 42.2k (-25% YOY). Consequently, CTR dropped from 2.9% to 1.2% despite average position increasing from 24.6 to 17.7. I’m not exactly sure what’s driving this divergence. Perhaps Google’s AI Overviews or agentic traffic are increasing impressions without driving associated clicks. ![Image](https://eugeneyan.com/assets/2025-search.webp "Image") Search traffic and trends in 2025 ## Goals for 2026 I’m keeping the same goals as 2025. I found myself stretching to meet the first two given my increased official scope at work, and I want the last two to solidify into lifelong habits. - **Write 6 substantive pieces** - **Prototype 4 apps in public** - **Health**: Weekly 5k run + weights + healthy diet - **Snowboarding**: Attempt a black run If you found this useful, please cite this write-up as: > Yan, Ziyou. (Dec 2025). 2025 Year in Review. eugeneyan.com. https://eugeneyan.com/writing/2025-review/. or ``` @article{yan20252025review, title = {2025 Year in Review}, author = {Yan, Ziyou}, journal = {eugeneyan.com}, year = {2025}, month = {Dec}, url = {https://eugeneyan.com/writing/2025-review/} } ``` Share on: ![](https://eugeneyan.com/assets/icon-twitter.svg) ![](https://eugeneyan.com/assets/icon-linkedin.svg) ![](https://eugeneyan.com/assets/bluesky.svg) ![](https://eugeneyan.com/assets/icon-facebook.svg) ![](https://eugeneyan.com/assets/icon-mail.svg) Join **11,800+** readers getting updates on machine learning, RecSys, LLMs, and engineering.