Operations & Supply Chain: interview questions and learning guide

Supply chain basics

A supply chain is a relay race: every handover must be smooth.

A supply chain moves goods from suppliers to customers. Teams balance stock levels against cost, plan from demand forecasts, and choose suppliers and carriers carefully so products arrive on time.

Interview tip: Use numbers: stock-outs avoided, cost saved, on-time delivery.

Process improvement

Great operations remove waste so people can do the valuable work.

Process improvement finds waste and variation and removes them. Lean focuses on flow and waste, Six Sigma on defects, and Kaizen on small daily improvements. Standard procedures keep the gains.

Interview tip: Tell a before and after story with numbers.

Inventory management and warehousing

A warehouse is a library: if books are not shelved by a clear system, nobody can find or trust anything.

Inventory is stock held to serve customers without delays. Too little stock loses sales and too much blocks cash and space. A good warehouse has clear receiving, put-away, storage, picking, packing and dispatch flows. Every item has a fixed location, and every movement is recorded in the system. Regular counts keep the system quantity equal to the physical quantity.

Interview tip: Say that accurate records matter more than a tidy look, because a tidy shelf with wrong system stock still causes stock-outs.

Procurement and vendor management

Buying is like choosing a long-term partner: price matters, but reliability decides if the relationship works.

Purchasing turns a need into delivered goods at the right quality, cost and time. It starts with a requisition, moves to quotations, comparison, negotiation and a purchase order. After delivery, the invoice is checked against the order and the receipt before payment. Good buyers also manage vendors over time with scorecards, audits and development plans. The aim is lowest total cost, not only lowest price.

Interview tip: Always talk about total cost and risk, not just the lowest quote, and mention a backup vendor.

Logistics and transportation

Logistics is the road system of a business: it only gets noticed when a jam happens.

Logistics moves goods from supplier to factory to customer in the right condition and on time. Choices include road, rail, sea and air, each with its own speed and cost. Trucks are booked as full loads or shared loads. Paperwork such as invoices, lorry receipts and bills of lading travels with the goods. Planners balance cost, speed and risk, and track every shipment until proof of delivery comes back.

Interview tip: Show you know the cost-speed trade-off and that delivery is closed only after proof of delivery is received.

Demand planning and forecasting

Forecasting is like a weather report: it is never perfect, but it still tells you whether to carry an umbrella.

Demand planning estimates what customers will buy so supply, stock and capacity can be ready. It uses past sales, trends, seasons, promotions and market news. Simple methods like moving averages work for steady items, while smoothing handles trends. Forecast error is measured and reviewed every cycle. In a monthly planning meeting, sales, finance and operations agree on one number and plan supply against it.

Interview tip: Say you measure forecast error and bias every month and fix the cause, rather than blaming the forecast.

ERP and SAP basics for operations

An ERP is one shared notebook for the whole company, so purchase, stores, production and accounts all read the same page.

An ERP system links departments through one database. When stores post a goods receipt, finance sees stock value and payables update. Operations people mostly use materials management, sales and distribution, production planning and warehouse modules. Master data such as materials and vendors must be clean, because every transaction depends on it. Users run actions through screens or transaction codes and need the right roles to do so.

Interview tip: Stress that bad master data causes most ERP problems, and that you check data before posting transactions.

KPIs and operational excellence

What you do not measure drifts; a KPI is the dashboard light that tells you something needs attention.

Operational excellence means running processes safely, reliably and at low cost, and improving them every day. KPIs make performance visible. Good ones are few, clear, tied to a goal and owned by one person. Examples are on-time in-full delivery, inventory turns and cost per unit. Teams review them in short daily meetings, walk the floor to see causes, and write standard work so gains stay.

Interview tip: Pick two or three KPIs, say who owns each, and give one example where a number led to a fix.

Find the bottleneck with data, improve forecasting, align suppliers, hold safety stock and communicate clearly.

Describe the problem, data and root cause, the change you made, the measured result and the new SOP.

Lead time is from the customer order to delivery. Cycle time is how long one process step takes to complete a unit.

FIFO issues the oldest stock first. FEFO issues the stock that expires first, important for food and medicine.

Ask why repeatedly, usually five times, to move from a symptom to the root cause, then fix the cause.

On Time In Full. The percentage of orders delivered on the promised date and in the full quantity.

Improve forecasts, set safety stock by demand variation, shorten lead times, and review fast and slow movers.

The slowest step that limits the whole output. Measure it, remove waste there, add capacity or rebalance work.

Ranking items by value: A items are few and high value, B are medium, C are many and low value. Control A items most closely.

Review quality, delivery record, price, capacity, certifications and references, then start with a small trial order and track scores.

Planning and managing the flow of goods from suppliers to customers, including sourcing, production, storage and delivery.

How many times stock is sold and replaced in a period. Higher turnover usually means efficient stock use.

FIFO uses the oldest stock first. LIFO uses the newest first. FIFO suits perishable goods.

Find the cause, improve planning, communicate with vendors, add buffer stock and track shipments daily.

3PL outsources logistics to a specialist provider. In-house means your own team and fleet handle it.

Lean removes waste. Six Sigma reduces variation and defects using data.

Review the data, discuss the cause, set clear expectations and penalties, find a backup supplier and escalate if no change.

Software that runs core processes like inventory, purchase and finance in one system. Name the system you used and what you did.