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2827 questions of the kind that actually get asked — in interviews, in architecture review boards, and by the person who has to run the thing at 3 AM. Every answer states the trade-off rather than the slogan, and says when the obvious choice is the wrong one.

All areas2827 Architecture Fundamentals91 Distributed Systems101 Data Architecture90 Cloud Architecture87 Networking86 API & Integration Architecture87 Reliability & Resilience99 Observability92 Performance & Capacity Engineering90 Security Architecture95 Cost Architecture & FinOps92 Business Architecture93 Architecture Communication91 Enterprise Architecture100 Legacy Modernization92 AI-Era Architecture96 Software Architecture & Engineering93 Architecture Patterns84 Architecture Decision-Making101 The Architect's Meta-Skills92 Delivery & Release Engineering103 Platform Engineering & Developer Experience92 Testing & Quality Architecture102 Data Platform Architecture98 Streaming & Real-Time Data93 Data Governance & Semantics91 Frontend & Experience Architecture101 Edge, Mobile & IoT98 Regulatory & Data Protection Architecture99 Assurance, Audit & Model Risk98
Difficulty Any beginner intermediate advanced

98 questions in Edge, Mobile & IoT.

  1. Constrained Protocols intermediate Multiple choice

    A battery-powered sensor on a cellular network holds an MQTT session. After quiet periods the server's messages stop arriving, though the device's socket is still open and sending works. Which change fixes it at the lowest energy cost?

    2 min answer mqttnatkeepalivebattery
  2. Constrained Protocols beginner Multiple choice

    A metered NB-IoT fleet must not record a reading twice, because readings drive a customer's bill. The team proposes QoS 2 so the broker delivers each publish exactly once. Which choice fits better?

    2 min answer mqttqosidempotencynb-iot
  3. Constrained Protocols intermediate

    A soil-moisture sensor runs on two AA cells, about 2,000 mAh usable. It wakes every 15 minutes, sends roughly 60 bytes, and sleeps. Sleep draw is about 10 uA. Each transmission cycle takes roughly 2 seconds at an average 30 mA while the radio is active. Estimate the battery life, and say which assumption you would attack first.

    3 min answer batteryduty-cycleenergyiot
  4. Constrained Protocols advanced

    An MQTT 5 broker cluster serving 120,000 sensors starts alerting on disk at 03:00 every night, and the oldest of those alerts is three weeks old. Publish rate is flat at roughly 900 messages per second, connected clients sit at 118,000, and the broker reports 340,000 sessions and rising. No messages are being dropped yet. What failed, and which design decision made it possible?

    3 min answer mqttsessionsbrokerqueueing
  5. Constrained Protocols intermediate

    Devices are battery-powered with intermittent low-bandwidth connectivity. What protocol properties matter, and what is usually chosen wrongly?

    1 min answer protocolsmqttcoappower
  6. CRDTs advanced

    A collaborative field-notes app uses a CRDT set per project so devices can edit offline and merge without a server decision. Two years in, projects that are heavily edited take 40 seconds to open on a mid-range phone and the local database is 900 MB. Nothing has failed. What is happening, and what would you have designed differently?

    3 min answer crdtstombstonesmetadatafigma
  7. CRDTs advanced

    A collaborative product must let several devices edit the same records, including offline. When are CRDTs the right answer, and when is server authority simpler?

    2 min answer linearcrdtsyncconflicts
  8. CRDTs advanced

    A team proposes CRDTs for a collaborative document editor. What do you check before agreeing?

    2 min answer crdtcollaborationtradeoffs
  9. CRDTs advanced

    An inspection app keeps each site's checklist in an observed-remove set CRDT and synchronises by sending the whole replica state on every reconnect. 6,000 devices on cellular, roughly 40,000 elements per site set, about eight reconnects a day. Roughly how many bytes per device-day, and what does the number rule out?

    2 min answer crdtsor-setdelta-statebandwidth
  10. CRDTs advanced

    Conflict-free replicated data types guarantee convergence without coordination. What do they cost, and when is the guarantee not enough?

    1 min answer crdtsconvergencecollaborationmetadata
  11. CRDTs beginner

    Two inspectors both work offline on the same site photo. One adds the tag "damp" and edits the caption; the other adds the tag "crack" and edits the same caption. After sync both tags are present and only one caption survived. The app uses the same CRDT library for both fields. Why did the same merge engine protect one field and silently discard the other?

    3 min answer crdtslww-registerdata-modellingoffline-first
  12. Device Identity advanced

    A fleet of devices has certificates expiring in two years. What must be true today for that not to be an incident?

    2 min answer device-identityrotationprovisioningrevocation