Kai Hendry's technical notebook
Notes on making
things work.
Cloud infrastructure, AI, and the things I learn along the way.
Latest writing
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The Hybrid Meeting Problem
Have we solved the problem of meetings with both in-person and remote attendees?
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Feather razor blades: a cheap way to shave
Japanese Feather blades and my German MÜHLE safety razor. My 2022 purchase worked out at about 32p per blade.
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My favourite desk lamp: Logitech Litra Beam
The Logitech Litra Beam doubles as a desk lamp and an automatic light for online meetings. A few niggles, and why I'd wait for a £60 deal.
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ESP With the Strongest WiFi Signal
I compared WiFi RSSI across three ESP boards I had lying around: an ESP8266 with a PCB trace antenna, an ESP32-D0WDQ6 with a folded PCB antenna sticking up off the module, and an ESP32-D0WD-V3 with a flush trace antenna. The one with the antenna folded up off the module won by ~10-20dB.
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Why Enterprises Struggle to Adopt AI
A running list of reasons the fast feedback loop that makes agentic AI work keeps getting bottlenecked and stalled inside large organisations.
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Two Heat Pump Surprises: Cylinder Standing Loss and a −40 °C Outdoor Sensor
A month into living with a Vaillant aroTHERM plus: measuring how fast the hot water cylinder cools down, and the day a power cut left the outdoor sensor reading −40 °C and the heat pump heating the house in August.
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Three Secrets Domains on Purpose
Why a large org keeps developer, CI and workload secrets in three separate systems — 1Password, GitHub secrets and AWS — and how short-lived credentials and least privilege hold it together.
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My Maui Jims Have New Nose Pads: NSP252
The nose pads on my decades-old glass-lens Maui Jims perished and the model number had worn off the frame. Julie and Scott at Maui Jim customer services worked it out anyway: NSP252, 14.3 x 7 mm. Buy it for life.
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Reading the Heat Pump Locally: eBUS Adapter Stick C6 and ebusd
Tapping the Vaillant aroTHERM plus eBUS with an eBUS Adapter Stick C6 and ebusd, for 678 local Home Assistant entities instead of a rate-limited cloud API — including the wiring, the MQTT flag that silently breaks discovery, and a heat pump model with no config file.
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Our First Air-to-Water Heat Pump: Vaillant aroTHERM plus
Notes, photos and costs from installing a Vaillant aroTHERM plus VWL 35/8.1 A air-to-water heat pump under the UK's Boiler Upgrade Scheme, plus wiring it into Home Assistant to chase cheap Octopus rates.
AI Infrastructure
All episodes →Build versus buy in the age of AI
Kai Hendry and Vincent De Smet debate build versus buy in the age of AI, infrastructure testing, agent workflows and the human bottlenecks in enterprise delivery.