iiinova — where your digital self keeps evolving

Martin Kleppmann @martin.kleppmann.com · 17/09/2026

There's a new Dinky Door in Cambridge! The cyclopunt – half cargo bike, half punt – best vehicle ever! www.dinkydoors.co.uk

A piece of miniature street art with the feet of people walking by out-of-focus in the foreground. The sculpture is a punt (a long flat boat) with the front and rear wheels of a cargo bike attached at both ends. The punt is loaded with parcels.

The cyclopunt from a perspective where you can see a bit of the street scene as well. It's located in Rose Crescent in central Cambridge.

4260

Martin Kleppmann @martin.kleppmann.com · 29/07/2026

lol thank you IEEE for giving me a good laugh (CC @mweidner.bsky.social)

BibTeX export of one of my papers from IEEE Xplore. The keywords field contains some plausible terms, but also some inexplicably odd ones, including "Dairy products"

3191

Martin Kleppmann @martin.kleppmann.com · 12/07/2026

So excited to be speaking at @localfirstconf.com in a few minutes!

Panorama photo of the stage and audience of Local First Conf

2931

Martin Kleppmann @martin.kleppmann.com · 20/06/2026

There's a special category of spam: dubious book promoters targeting authors. Mostly the emails are just lazy AI slop. But occasionally they are amusing, such as this one, praising the "character development, psychological depth" of a technical book that definitely has none of either of those 🤪

Screenshot of an email:

"Dear Martin Kleppmann,

I hope this message finds you well.

My name is Johnson, and I am a Marketing Representative with USA TODAY Newspaper.

After carefully reviewing your work, we were impressed by the themes, character development, psychological depth, biography, encyclopedia value, and overall literary contribution presented in your book. Your work stood out to our editorial and marketing team, and we believe it would strongly connect with our readers and audience."

6332

Martin Kleppmann @martin.kleppmann.com · 29/05/2026

Designing Data-Intensive Applications contains a joke about datacenters in space, since at the time of writing, that seemed like an absurd thing to even contemplate. And yet, here we are, with the biggest ever IPO prospectus promising orbital datacenters. I guess I'll have to update that paragraph.

Screenshot of a paragraph from my book, Designing Data-Intensive Applications:

"Fault tolerance is always limited to a certain number of certain types of faults. For example, a system might be able to tolerate a maximum of two hard drives failing at the same time, or a maximum of one out of three nodes crashing. It would not make sense to tolerate any number of faults; if all nodes crash, nothing can be done. If the entire planet Earth (and all servers on it) were swallowed by a black hole, tolerance of that fault would require web hosting in space—good luck getting that budget item approved."

411312

Martin Kleppmann @martin.kleppmann.com · 26/05/2026

Apparently Amazon will not allow me to read the reviews of my own book

Screenshot of an email from Amazon that reads:

Hello,

Thank you for your request to see more customer reviews.

Your request is not approved at this time, and you will see a limited selection of customer reviews.

To learn more about this decision, see our Conditions of Use. If you disagree with this decision, please contact community-content-access-appeals@amazon.com with additional details about your request.

Thank you for your understanding.

1015116

Martin Kleppmann @martin.kleppmann.com · 17/03/2026

Looking forward to giving the morning keynote at QCon London in half an hour

A massive conference hall with many rows of empty chairs, just one person sitting in the front row

Large stage at the front of the conference hall

3631

Martin Kleppmann @martin.kleppmann.com · 04/03/2026

Just received my author copies of the second edition of DDIA! After years of seeing it only on-screen, holding the final print book in hand is very special. @chris.blue

A print copy of Designing Data-Intensive Applications, 2nd edition

2037017

Martin Kleppmann @martin.kleppmann.com · 03/03/2026

Oh, is *that* your favourite breakfast, dear Waitrose?

Supermarket shelves labelled “breakfast favourites”, and the shelves contain bottles of whisky and gin

3527

Martin Kleppmann @martin.kleppmann.com · 18/02/2026

The second edition of Designing Data-Intensive Applications, by myself and @chris.blue, is finished and sent off to the printers! Ebooks should be available in the next week, and print books in 3–4 weeks. Sigh of relief. 😅 (BTW, this is a good opportunity to support your favourite local bookshop!)

Book cover of "Designing Data-Intensive Applications, 2nd edition". It has a similar wild boar on the cover as the first edition, but it uses O'Reilly's new cover design, and the boar is now slightly colourised.

27674140

Martin Kleppmann @martin.kleppmann.com · 05/02/2026

I finally got to visit UC Berkeley for the first time today! Gave a talk and had good discussions about distributed systems with @joehellerstein.bsky.social & others from his group

Soda Hall, the home of the Berkeley CS department

The Campanile (bell tower) at UC Berkeley in front of blue sky

3370

Martin Kleppmann @martin.kleppmann.com · 06/01/2026

The rise and fall of Stack Overflow. Graph shows number of questions posted per month. Discussion: news.ycombinator.com/item?id=4648...

Graph of number of questions posted per month on Stack Overflow. It starts at 0 in 2008 and rises roughly linearly until about 2014. Then it's flat for a few years and begins gradually declining from about 2018. From 2021 until now it falls steeply, and it eventually goes very close to zero.

36710

Martin Kleppmann @martin.kleppmann.com · 24/12/2025

We got a white Christmas (with a light dusting of snow) in southern Germany! Merry Christmas to all who celebrate it! 🎄❄️

Me looking cold, pushing a sleeping toddler though a park on a buggy. There is a thin layer of snow on the ground. The toddler is anonymised with an emoji over the face.

A burning red candle on a Christmas tree, decorated with straw stars, corn dollies, straw angels, and other things

4700

Martin Kleppmann @martin.kleppmann.com · 14/10/2025

Anyone know why you can’t take coconuts, spices, or umbrellas on the plane?

Photo of a sign at Delhi airport that lists the items that are prohibited in hand luggage. Besides the usual ones like knives, scissors, and firearms, there are also some more surprising prohibited items like coconut, umbrella, fork & spoon, and spices.

12161

Martin Kleppmann @martin.kleppmann.com · 13/10/2025

I got to go to India for the first time for my brother’s wedding. What a magical experience! And a nice opportunity to wear some colourful Indian outfits 😊

Me wearing a golden yellow outfit for Haldi

Me with Mehendi (henna tattoo) on my hand, wearing a dark green kurta with sequins

Me in a richly embroidered light blue/grey sherwani and wearing a light green turban

91092

Martin Kleppmann @martin.kleppmann.com · 23/08/2025

Stumbled across some old photos of the first computer I built myself, circa 1998. I installed it in a metal tool box into which I cut some holes. The handle was very convenient for carrying the computer to LAN parties.

A big red toolbox. At one end, there are openings for a 3.5” floppy drive, a CD drive, a removable hard disk bay, as well as a rotary dial from an old telephone (not functional, only decorative), a key switch, and a Linux sticker.

The other side of the toolbox. On one side is an opening for the power supply. In the lid there’s a big fan. At the end are the motherboard connectors (PS/2 for keyboard/mouse, etc), graphics card, network card, USB card, and sound card.

The box with the lid lifted, showing the computer components installed on the inside.

Me carrying the big red computer box by its handle

2336929

Martin Kleppmann @martin.kleppmann.com · 02/08/2025

It’s the instructions for “drop of liquid above five triangles in random orientations, separated by a horizontal line”, which I can only guess means “cleaning”

Same photo as before, but now showing the heading above the first panel

290

Martin Kleppmann @martin.kleppmann.com · 02/08/2025

Our new Philips egg cooker came with no textual instructions, only pictorial ones. How many people without a chemistry degree are likely to figure out what “4% AcOH” means? (Spoiler: it means “vinegar”)

Photo of instructions for an egg cooker. In the first panel, you are instructed to pour 30ml of “4% AcOH” and 30ml of an unspecified liquid (assumed to be water) into the device.

2115319

Martin Kleppmann @martin.kleppmann.com · 13/07/2025

Surprisingly polite graffiti at the local skate park

Red graffiti that says: “SIR STARMER” IS A TORY IN A RED TIE

Blue graffiti that says: BE PROUD OF WHO YOU ARE ❤️

Orange graffiti that says: STOP LETTING POLITICIANS THAT DONT CARE ABOUT US BACK INTO OFFICE

2364

Martin Kleppmann @martin.kleppmann.com · 04/07/2025

One way in which AI enriches my life is that I can go from “ooh, that’s a funky looking caterpillar” to a fun Wikipedia rabbithole in a few seconds, thanks to iOS’s automatic plant and animal detection in photos. This is a cinnabar moth caterpillar, apparently

Three caterpillars, coloured in bright yellow and black stripes, feeding on a plant in front of a brick wall

1282

Martin Kleppmann @martin.kleppmann.com · 03/07/2025

The Cambridge Peregrines folks caught it and brought it back to the nest on the roof

One person pinned the bird to the ground, another taking photos for documentation

Baby kestrel held safely in the hand of the person who rescued it

2333

Martin Kleppmann @martin.kleppmann.com · 03/07/2025

Fledgling kestrel in the courtyard of our department building!

Kestrel sitting on the back of a wooden bench in front of office windows

1611

Martin Kleppmann @martin.kleppmann.com · 02/07/2025

ATM left in maintenance mode or something? 🤔

ATM screen showing a menu with options: REPLENISH, ACCESS, TRANSFER, FAULT DISPLAY, MISC FUNCS, CONFIGURE, DIAGNOSTIC, EXIT. The reflection shows me wearing a bike helmet and sunglasses taking the photo

3200

Martin Kleppmann @martin.kleppmann.com · 02/07/2025

Nice idea by @lambda.bsky.social to make mugs for co-authors celebrating our papers 🎉☕️

Two exceptionally geeky-looking mugs. The left one has an illustration of a user discovery service for anonymity networks printed on it, and the right one has some box-and-whisker plots showing performance data from another paper

0510

Martin Kleppmann @martin.kleppmann.com · 28/06/2025

Summer is here, exam/dissertation marking is done, and we’ve already harvested 2kg of raspberries and turned them into jam ☀️🎉

1771

Martin Kleppmann @martin.kleppmann.com · 28/06/2025

Very cool that the university bus service has a numberplate UNI4BUS. There’s just one problem… it’s on the U2 bus line, not U4

6171

Martin Kleppmann @martin.kleppmann.com · 27/06/2025

(paywalled article, here are screenshots)

Screenshot of the beginning of the article

1130

Martin Kleppmann @martin.kleppmann.com · 07/06/2025

Nice impressions from @localfirstconf.com (photography by Susanne Elsässer)

Johannes Schicking, Nik Graf, Leo Stewen, and myself huddled around a laptop with stickers on it. More people in the background

Me on stage speaking as part of a panel, sitting next to Aaron Boodman

Panel discussion in front of an audience of hundreds at Local First Conf

Me standing and talking to Sam Willis in the conference hallway

1353

Martin Kleppmann @martin.kleppmann.com · 23/05/2025

Got the cover design for the second edition of DDIA from the publisher. Now just need to finish the effin’ manuscript…

Book cover for Designing Data-Intensive Applications, 2nd edition, by Martin Kleppmann and Chris Riccomini. It has a coloured picture of a jumping Indian Wild Boar (similar to the first edition, but not identical).

923327

Martin Kleppmann @martin.kleppmann.com · 14/05/2025

Nonmonotonic clock spotted in the wild: I left `ping` running in the background on my laptop while it went to sleep, and later I found that my minimum round-trip time was a negative number!

Screenshot of the last few lines of pinging google.com. 21451 packets transmitted, 0.6% packet loss. Round-trip min = -289.777 ms, avg = 40.446 ms, max = 3763.579 ms, stddev = 112.306 ms

28912

Martin Kleppmann @martin.kleppmann.com · 02/05/2025

Wearing mysterious logos like it’s some sort of secret cult

1390

Martin Kleppmann @martin.kleppmann.com · 30/04/2025

Folks at Google: there's no longer a button to get the PDF of your research papers directly from your website. Instead you have to do a hop through Google Scholar. Is that intentional? Seems worse than it used to be before.

Screenshot of the Percolator paper on the Google Research website. There are buttons for "Google Scholar" and "Copy Bibtex", but none to download the actual paper!

2562

Martin Kleppmann @martin.kleppmann.com · 03/04/2025

Worrying message… anyone know why this would happen, even though I’m not (knowingly) running any screen recording/sharing app, and no external displays connected?

macOS lock screen on a laptop. At the top is some text saying “Your screen is being observed”

9192

Martin Kleppmann @martin.kleppmann.com · 13/03/2025

I’ve cycled past this residential house on Adams Road hundreds of times, but only noticed today that it appears to have a personal astronomical observatory on the roof. As you do in Cambridge, of course.

3785

Martin Kleppmann @martin.kleppmann.com · 12/03/2025

Nobel laureate Sir Demis Hassabis, a graduate of our department, came back to Cambridge to give a talk today. I was impressed by his thoughtfulness and the positive potential of applying AI to the natural sciences.

Demis Hassabis speaking in front of a packed lecture theatre. The current slide shows some prospective areas in which AI is being applied: identifying eye disease from retinal scans; discovery of new materials; fusion plasma containment; faster matrix multiplication; weather prediction; quantum error correction.

2511

Martin Kleppmann @martin.kleppmann.com · 02/02/2025

Got to play around with an infrared camera, which is great fun. Here's what our heat pump looks like

Infrared image of a heat pump. The big fan is just above 0ºC, the warm part of the unit and the insulated pipes bringing hot water into the house are about 7ºC on the outside, and the environment temperature is about 3ºC.

41201

Martin Kleppmann @martin.kleppmann.com · 19/01/2025

We recently replaced the gas boiler at our house with an air source heat pump. Very happy with it so far. If anyone in the UK is thinking of doing the same, I can recommend www.heatgeek.com

A Vaillant air source heat pump attached to a brick wall

1662552169

Martin Kleppmann @martin.kleppmann.com · 28/12/2024

Got a bottle of wild boar wine for Christmas! Does the picture on the label seem familiar? In case you’re wondering, it’s taken from an out-of-copyright book: General Zoology by George Shaw, vol. ii, part 2, page 458, published in 1801. archive.org/details/p2ge...

Me holding a bottle of red wine. On the label is an image of a jumping wild boar — the same as on the cover of my book, Designing Data-Intensive Applications

1332516

Martin Kleppmann @martin.kleppmann.com · 07/12/2024

Yesterday I went to the funeral of Peter Cowley, who helped me start my first company in 2007. Glad I got to meet him one last time a month ago. He specifically wanted Meat Loaf’s “Bat out of Hell” to be played at his funeral — what a legend. His memoir is well worth reading too www.ps-pg.com

Selfie of me with Peter, weakened by cancer but still smiling (slightly)

01011

Martin Kleppmann @martin.kleppmann.com · 18/11/2024

Time to show off your laptop stickers!

7502

Martin Kleppmann @martin.kleppmann.com · 16/11/2024

In June Elon posted this graph of the rate of likes on X. It doesn't have a unit on the y axis, but it's plausible to assume that it's events/sec. If that is true, X in June was handling about 20k likes/sec. For comparison, Bluesky is now handling about 700 likes/sec during the busy part of the day.

A graph showing the rate of likes on X over the course of a couple of hours on 12 June 2024. It fluctuates between about 17k and 20k; the y axis doesn't have a unit. A second line shows a comparison to the prior week, which is slightly lower. There are strange unexplained spikes on the hour every hour.

A graph showing the rate of various types of events on Bluesky over the last day. At peak there are about 800 follow events and 700 like events per second (note the likes are scaled down by a factor of 5; the right-hand y axis is for likes).

1455176

Martin Kleppmann @martin.kleppmann.com · 02/11/2024

Okay, let's try a revised version of the Bloom filter diagram with 75% fewer bits, a linear layout for the bits, and 25% fewer arrows. Is this one better? Design constraints: must be printable in black&white, should be compact so that it doesn't take too much space in the book.

Illustration of how a Bloom filter works. At the top are two keys that exist in the Bloom filter; for each we show the hash as a 12-bit binary number broken up into 3 groups of 4 bits. In the middle are 16 boxes each representing one bit. The boxes are numbered to 0 to 15, and each of the 4-bit values is interpreted as an index into the array of boxes. There are arrows from each 4-bit value to the corresponding box, and the boxes with an incoming arrow have a 1, whereas the others have a 0. At the bottom is a key being queried, which also has a 12-bit hash, and the arrows from the three 4-bit parts of that hash also point at the appropriate boxes.

2116012

Martin Kleppmann @martin.kleppmann.com · 02/11/2024

For the second edition of Designing Data-Intensive Applications we want to add a brief explanation of what a Bloom filter is (even though it's quite a well-known concept, we don't want to assume readers already know it). Here's my attempt at showing it diagramatically. What do you think?

Illustration of how a Bloom filter works. At the top are three keys that exist in the Bloom filter; for each we show the hash as an 18-bit binary number broken up into 3 groups of 6 bits. In the middle are 64 boxes each representing one bit. The boxes are numbered to 0 to 63, and each of the 6-bit values is interpreted as an index into the array of boxes. There are arrows from each 6-bit value to the corresponding box, and the boxes with an incoming arrow have a 1, whereas the others have a 0. At the bottom is a key being queried, which also has an 18-bit hash, and the arrows from the three 6-bit parts of that hash also point at the appropriate boxes.

2115821

Martin Kleppmann @martin.kleppmann.com · 23/10/2024

I get the strangest emails. Someone keeps sending me something that appears to be… Chinese poetry? Presumably this is just a harmless crank?

Screenshot of an email (sender's contact information redacted) with the following text:

Dear University of Cambridge:
A bundle of trichromatic light&A compulsory course
pursuing the light then meet，and bathing in the sunshine and walking together.
Please find the attached file for details.

regards.
Zhou Yanlong
10.23,2024/Autumn
Harbin～Beijing China
[WeChat username and phone number redacted]

剑桥大学您好：
夫以铜为镜，可以正衣冠，以古为镜，可以见兴替，以人为镜，可以知得失。

聚精【一堂心课 VS 一城一镜】会神
北京（史鉴）～哈尔滨（冰鉴）
一方水土、一方城…
一方精气、一方神…
一城、一脉、一树、一路…
一镜、一心、一沁、一沐…
史鉴&冰鉴：一路向北，彻骨感悟；
｛心沁愈、寒沐面、凝慧神，正衣冠、见兴替、知得失｝。

【一束三色光】&【一堂必修课】
尘劳迥脱事非常，紧把绳头做一场。
不经一番寒彻骨，怎得梅花扑鼻香。
☘️欢迎您：一堂心课&聚精会神；
️️诚邀偕作、共赢偕行。

致礼
周彦龙

2024年10月23日/秋

中国.北京～哈尔滨

Screenshot of Google Translate output of the email, with the following text:

Hello, Cambridge University:
A man can use copper as a mirror to adjust his clothes and hats, use the past as a mirror to see the rise and fall, and use people as a mirror to know gains and losses.

Concentrate [One Heart Lesson VS One City One Mirror] Meet the Spirit
Beijing (Shijian) ~ Harbin (Bingjian)
One land and one city...
One spirit and one spirit...
One city, one vein, one tree, one road...
One mirror, one heart, one infusion, one bath...
Shijian & Bingjian: Going north, feeling deeply;
{Heart is infused, face is bathed in cold, wisdom is concentrated, clothes are adjusted, rise and fall are seen, gains and losses are known}.

【A beam of three-color light】&【One compulsory course】
Get rid of the dust and labor, things are not ordinary, hold the rope tightly and do it.
Without going through a bone-chilling cold, how can the plum blossoms smell fragrant.
☘️Welcome: One Heart Lesson & Concentrate;
️️Sincerely invite you to work together, win together and walk together

With regards
Zhou Yanlong

October 23, 2024/Autumn

Beijing, China~Harbin

1230

Martin Kleppmann @martin.kleppmann.com · 19/09/2024

If you see this, post a butterfly to celebrate 10 million users on Bluesky. 🦋

Peacock butterfly on a purple flower. Photo taken with phone camera

0240

Martin Kleppmann @martin.kleppmann.com · 17/09/2024

Since I’ve been advising the Bluesky team since long before it launched, I’ve been enjoying a front-row seat in the whole process 😄

My “celebrating 10M users” graphic. I am user number 7.

527514