Dispatches from the work in progress
An MQTT broker proves who delivered a command, not who wrote it. Why we sign every device command with a KMS-held key, bind it to one device, and why our first key switch was a wall of rejections.
LPDDR4 routing is decided before the first trace is drawn. The SoC vendor gives you four numbers that drive everything else: 40 ohm single-ended and 80 ohm differential targets with a plus or minus 10 percent window, a total route delay ceiling near 250 ps, and intra-pair skew
Intro Some health signs in dogs show up at one specific time: right after a meal is one such crucial time. and panting or coughing are such crucial signals. Vets know this, and one of the first things they want to know about a cough is whether it happens consistently
Our mobile measurement partner reported nearly every install as organic while we were paying for install campaigns on two major networks. The media-source field was never filled once. The cause was not one bug: 6 faults, 3 in app configuration and 3 in our own attribution code, each independently
Matte, satin and gloss are three gloss bands, and each band behaves differently under fingers, scratches and light. Measured at 60 degrees, matte reads under 10 GU, satin reads about 10 to 40 GU, and gloss reads above 70 GU. In our illustrative bench set, a 500-cycle abrasion test
Our new camera module, running on its evaluation board, now classifies dog sounds on its own microcontroller. It turns the microphone into 16 kHz audio and computes a 64-band log-mel spectrogram on the CPU in about 320 µs per frame. Every 480 ms, an int8 eight-class network
A DynamoDB Query never returns more than 1 MB of data per call, no matter what Limit you pass. In our test, a Query with Limit=100000 on a 10,000 item partition returned 2,537 items and no error. The only sign that 7,463 items were left behind
A carrier board that accepts add-on boards it has never seen needs a power budget per slot, a current limit per slot and a negotiation step before any main rail turns on. On our AM62A7 carrier, a per-slot eFuse with a 4 ms soft-start cut add-on
1. The ask: tell ops the moment a pet tag order is paid Our company sells pet tags (QR tags that clip onto a pet's collar) through a Flutter mobile app. The operations team wanted to know the moment a tag order was paid, instead of checking an
A Query is not automatically cheap. In a test partition of 6,000 pet documents, a Query that filtered on pet_id read all 6,000 items and used 319 read capacity units to return 3. The same request against a composite sort key, OWNER#<owner>#PET#<
For a stacked shipping carton, C flute is the safer pick over B and E. In our illustrative sizing of a 400 × 300 × 200 mm carton, with the same 5.6 kN/m edge crush grade on all three, C flute carried 2,460 N of lab box compression strength,
Three background jobs, none of them serving a single user request, consumed nearly all of the DynamoDB read capacity on our production account. One scheduler table absorbed a GetItem count in the millions over a single week. A second job read a full batch from every index shard on every
When One Field Breaks the Contract: Fixing Pet Allergy Data Types A field that stores a pet’s allergies might look simple. It could be a list of strings, such as ["Chicken", "Peanuts"]. But what happens when one part of the system expects a list, another
The reliable way to send large files over MQTT is to not put them in MQTT at all. AWS IoT Core caps a single publish at 128 KB, so on our pet bowl the MQTT connection carries only a small request, the cloud answers with a presigned S3 POST, and
Few of our smart bowls went deaf for hours while every dashboard stayed green. The cause was one assumption almost every MQTT client invites you to make. They kept sending weight readings every few seconds. The fleet view showed them online. The cloud could see every one of them. But
