Systems that model the physical world, where recorded state diverges from reality by default and reconciliation is continuous rather than exceptional.
12 published across 7 topics.
Logistics domain fundamentals59 short answers on one page, for revising rather than studying.The end-to-end flow, milestones, and the event model that reports it.
It depends entirely on where it stopped, because silence is normal on a long line haul and alarming between two hand-offs that should be minutes apart. The design that answers it is an expected next event with a deadline per milestone, rather than a threshold on time since the last scan.
Model the journey as milestone events, each carrying both the time it happened and the time you recorded it, and derive current status by projecting that set in a fixed milestone order rather than storing a mutable column, because events arrive late, twice and in the wrong sequence.
Receiving, putaway, picking strategies, packing and the WMS.
Pick strategy follows from order profile and layout because travel dominates picker time, and the WMS is real-time because a person is standing in an aisle waiting for their next task, so task dispatch has a latency budget and a dispatched task cannot be silently recalled.
Block the location first so nothing allocates against a figure you have just disproved, then correct it as a recorded adjustment with a reason rather than an edit. Accuracy is maintained continuously by cycle counting, because stock records drift even in a well-run warehouse.
Load planning, vehicle routing as a heuristic problem, and carrier selection.
Usually nothing is wrong with the solver: it is optimising against a model missing constraints the planner knows and never told it, so the plan is optimal and unrunnable. The fix is to capture the overrides as data and turn the recurring ones into constraints, rather than to improve the objective.
You stop pursuing optimality and engineer for a wall-clock budget: build a feasible plan with a construction heuristic, improve it with local search or a metaheuristic until the clock runs out, and model the constraints that genuinely bind, which are time windows, capacity and statutory driver hours.
Slotting and delivery promises, driver apps, proof of delivery and failed attempts.
A slot shown at checkout has to be a reservation against remaining route capacity measured in minutes rather than a count of orders, and the flow behind it needs an offline-tolerant driver app, proof of delivery sized to the risk, and a designed path for the attempt that fails.
Treat the device as a first-class writer rather than a cache: it generates its own identifiers, records two timestamps per event, and queues durably until the network returns. Every submission carries an idempotency key because retries are certain, and genuine contradictions go to a human.
Scan events, estimated arrival, exception detection and customer communication.
Translate scans into a small set of customer-meaningful states, expect long silences and out-of-order uploads, never let a displayed status move backwards, and publish an arrival estimate with its uncertainty made visible rather than a single confident time you will miss.
Demand forecasting, safety stock, replenishment and the bullwhip effect.
Safety stock is the inventory you hold to buy a chosen service level against forecast error over the replenishment lead time, so it scales with the variability of demand and of lead time; the bullwhip arises because each tier reorders from its own buffered demand rather than the real one.
Cross-border documentation, duties, and compliance screening.
The code sets the duty rate, the controls that apply and whether the goods can move at all, so two codes mean two different amounts of tax paid on identical goods. It is the importer's legal responsibility rather than the freight forwarder's, and inconsistency is what an audit looks for.
The goods need a commercial invoice and packing list that agree, a defensible tariff classification and country of origin, an Incoterm fixing who pays duty and tax, and a completed restricted-party and export-control screen that blocks release rather than warning after despatch.