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
Several people, one room microphone: speaker labels are available, but reliable names still require enrolment, context or human review.
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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 →Always-on agents, real-world bottlenecks
Always-on agents promise freedom, but reviews, CI, model costs and human accountability still shape what we can build.