Happy data privacy day,!

To commemorate today's data privacy day, I gave a 60-min talk about data privacy at work, where I covered:

• Defining privacy
• Why privacy matters
• Debunking privacy myths
• Practical privacy tips

It was geared towards an audience with general interest but low technical knowledge about the space, so I kept the contents pretty high-level and only offered tips centered around easy but significant wins (ex: stop using Google Chrome). I also made heavy use of memes for my images to keep the conversation from getting too serious.

A total of around 40 people participated, and I think it was received pretty well and it generated some pretty interesting discussions. I enjoyed sparking conversation about the topic of data privacy, and I hope I achieved my aim to have the listeners come out of the talk with a better idea of why privacy matters, and the small things they can do to protect their data.

If you were to do something similar, what other topics would you cover?

I recently bought a pair of Primus Flows from ReVivo and I thought I would do a quick review of the process and the shoes.

Buying shoes from ReVivo

I bought a pair of the Primus Flows with the Good condition. The 4 conditions are explained on ReVivo's website as follows:

We offer four conditions of footwear on ReVivo, and our prices reflect the level of wear and repair the products show. Never Worn is like new, while Excellent will show very minimal, if any, signs of wear. Great will show some signs of wear and repair, while Good have noticeable signs of wear and repair such as marks, scuffs and/or patches. No matter its condition, all our refurbished footwear is thoroughly cleaned and fully functional.

I was slightly concerned about the Good condition shoes, but I figured that going on a couple of runs would make even new shoes eventually look similar, so I decided to take the plunge. The Primus Flows currently retail for 170 EUR on Vivo's website, while a pair of the Good condition on ReVivo is 87 EUR (a 49% discount), so it seemed like a pretty good deal. I live in the EU, and the standard shipping from the UK came out to be 11 EUR, making my total 98 EUR.

I placed the order on 2025-09-09, and it was shipped by ReVivo on 2025-09-11. I then received the shoes on 2025-09-15.

The shoes came in a single ReVivo-labeled box, and they were not wrapped or packaged in anything else, which was fine for me.

When inspecting the condition of the shoes, Vivo's description of "noticeable signs of wear and repair such as marks, scuffs and/or patches" seemed to be pretty accurate. There were some signs that the shoes had been worn in the past, especially in the insole-less insides and the outsoles of the shoes. But that seems to be more than worth the 49% discount, so I don't mind the aesthetic blemishes at all.

Overall, I'm pretty satisfied with my first purchase on ReVivo, and I will keep my eyes on the site to see if I can buy some of the Vivo models I'm looking at in the future.

Initial impressions of Primus Flow

My all-time favorite hobby is trail running, for which I have been using the Primus Trail Knit FGs. The shoes have gotten me through some epic trail runs, including a 50K trail race and 63K solo trail run. But I recently moved to a country in the EU without any mountains, so I am unfortunately now relegated to pounding pavement for running, which I don't find to be as enjoyable.

I had been using the Vivo Primus Knit without the insoles as my daily shoe and road running shoe, which I have really enjoyed. But now that I'm training for my 4th road marathon, I am starting to increase my road mileage, and I have started to need a bit more protection for my joints plus a dedicated road running shoe. I was debating between the Primus Lite 3.5s and the Primus Flows, and I settled on the lightweight shoes designed specifically for road running.

For sizing: I wear size 43 on my Primus Trail Knit, Primus Lite All Weather, but size 42 on my Primus Lite Knit without the insoles. I went with size 43 on the Primus Flows, and they fit great.

I've taken them out on 4 runs (1 speed interval and 3 recovery runs) so far, and I like them so far as road runners, but I won't be using them as my everyday walking shoes.

The pros of the shoes:

• Extremely lightweight at 159g for size 42
• The midsole provides some protection, so I'm not afraid to use them for long runs
• Great heel lock that helps the foot stay in place while running

The cons of the shoes:

• The outsole is not really flexible and doesn't have as much ground feel due to the midsole, making it not so great for everyday walking shoes
• The insides of the heel are made up of leather-like material, which helps heel lock, but it catches your socks when taking the shoes off. These are the only pair of shoes where I have to tie and untie the shoelaces each time I take them on/off.
• The uppers are not as breathable as my knit shoes (regular Primus Knit and Primus Trail Knit), despite being almost see-through

If I had to get a single shoe, I would stick with either the regular Primus for weight (225g) or the Primus Knit for comfort (246g). But since I'm doing a fair bit of road running, I'm happy to have a dedicated shoe for road running, and the Primus Flows seem to work well for that purpose.

Charts

• Boxplot of SOT on stock vs. GOS
• Complete visualization of SOT on stock vs. GOS
• GOS SOT over a month
• Stock SOT over a month

Conclusion

• On my Pixel 8, stock seems to offer better battery life compared to GrapheneOS, with a mean SOT of 06:51 on stock, versus a mean SOT of 06:03 on GOS.
• I can't be sure where the difference in battery life is coming from, but it may be due to stock's adaptive battery function that is not available on GOS.
• However, the slight increase in battery life on stock is not worth the amazing privacy and security benefits that GOS provides over stock, so I will be sticking to GOS.

Context

• I wrote a similar post to this one based on the tracking and analysis I did while I tested out stock Android before switching to GrapheneOS (Lemmy), and I wanted to complete my battery tracking by also seeing how GOS battery life compares to stock Android.
• Similar to my testing while on stock, I used my phone as normal on GOS, with the below configurations:
  • LTE only (I don't have a 5G plan)
  • 120hz refresh rate
  • Owner user, with separate work profile managed by Shelter
  • Sandboxed Google Play Services enabled for both main profile and work profile on the owner account
  • Dark mode
  • Bluetooth on, always connected to my Galaxy Watch 6 Classic and very often connected to other BT audio devices
• With the above configurations, I used the phone normally, then took screenshots once I got the low battery warning notification at 20%. I started including the screenshots for the per-systems screen after seeing that the SYSTEM (IDLE) stats would be useful to track, but since I only have these datapoints for 11 charging cycles on GOS, I've excluded them from the analysis, although I am including the per-systems battery usage screen for reference.

Personal usage patterns & use-case

• I try to achieve a balance between privacy and convenience, so I am using Sandboxed Google Play Services and only use one user. However, I minimize unnecessary permissions and try to install only FOSS apps on my main profile while installing as many proprietary apps into my work profile as possible.
• The way I used my phone across stock Android and GOS was quite similar, although I did try to take advantage of GOS features whenever possible, such as enabling memory tagging, toggling off network permissions for apps that don't need them, etc.
• Depending on your privacy threat model, you can use a more strict setup without sandboxed Google Play Services, which may actually decrease battery life due to constantly active web sockets, or you may use multiple users to compartmentalize different apps into different profiles, which may save more battery versus my compartmentalization via Shelter.

Notable observations

• Although I got less SOT in general using GOS, I was still able to push the SOT past 9 hours with an idle time of 26:58 on my heaviest day (link), which is amazing battery life.
• Streaming music on Spotify seems to be a huge battery hog, and other Pixel users have noticed the same (link). The worst SOT I got, which was 02:13, seems to be largely due to at least an hour of music streaming on Spotify.
• On a related note, the background time tracking of Spotify is unreliable, as there were days when I was streaming music for about an hour (link), which led to a 10% battery decrease, but the battery usage screen says Spotify was active in the background for less than a minute (link).

Data & screenshots