Using this in a case: operations and cost cases
What to ask, what to calculate and what to say when a case is about capacity, cost or risk, with a full worked case from a parcel hub in Dubai.
Key takeaways
- Operations and cost cases reward the same habit: follow the work step by step, find the number that limits output or drives cost, fix the cheapest thing first, and test the answer against a worse future before you recommend spending money.
- The strong answer leads with the decision, gives the numbers that drive it, tests a worse future, and names the signal that would change the answer.
- Common mistakes in operations and cost cases: Jumping to the expensive answer (a new machine, a new plant) before checking the bottleneck and the cheap fixes.
Key idea
Operations and cost cases reward the same habit: follow the work step by step, find the number that limits output or drives cost, fix the cheapest thing first, and test the answer against a worse future before you recommend spending money.
What to ask first
- What is the goal: more output, lower cost, faster service, or fewer errors? By how much and by when?
- What are the steps, and what can each one handle? Is demand above or below the slowest step?
- Where are the costs: people, machines, materials, stock, defects?
- Is the problem steady, or only at peaks or in some seasons?
- What could go wrong, and how sure is the demand forecast?
What to calculate, and which lesson in this module it comes from
- Output = the lower of demand and the slowest step; the value of an hour at the bottleneck (capacity and bottlenecks).
- OEE as lost minutes, utilization, and the wait it causes (productivity and utilization).
- Lead time, cash in stock and its carrying cost; extra output from the same assets (lean basics).
- Prevention against inspection against failure costs (cost of quality).
- Net yearly saving, payback, and the volume needed to pay back (automation).
- Expected loss of each risk, and the base, upside and downside results of each option (risk and scenarios).
Worked case
A parcel hub in Dubai that cannot cope with peak season
The prompt
Interviewer: "A delivery company runs a parcel hub in Dubai, open 20 hours a day. In the 90-day peak season, 200,000 parcels arrive a day. The hub cannot handle them all, so the overflow goes to a subcontractor, which costs AED 5 more per parcel. The step capacities are in the table with this case. Management wants to buy an automated sorter for AED 40 million. What do you recommend?" (Fictional company, illustrative figures.)
The structure
- Overflow cost = (peak demand minus hub output) x peak days x AED 5
- Hub output = the lower of demand and the slowest step
- Key: Cheap fix first: raise the sorting lines' OEE
- Then the sorter: net saving and payback
- Downside: what if peak volume is lower?
The exhibit
| Step | Parcels per hour | Parcels per day (20 hours) |
|---|---|---|
| Unload trucks | 12,000 | 240,000 |
| Sort (manual lines) | 8,000 | 160,000 |
| Load delivery vans | 11,000 | 220,000 |
Working it through
1. Pin the question and find the bottleneck
The goal is to stop paying for overflow at the lowest total cost. Output is the lowest of demand and the three steps; sorting limits the hub.
Hub output today (parcels a day):min(200,000; 12,000 × 20; 8,000 × 20; 11,000 × 20) = 160,0002. Cost of the problem
40,000 overflow parcels a day, for 90 days, at AED 5 each, in AED millions.
Overflow cost a year (AED millions):(200,000 - 160,000) × 90 × 5 ÷ 1,000,000 = 183. Cheap fix first
The interviewer says the lines lose about an hour in eight to jams and restarts. Fixing chutes and training (AED 2 million once) lifts sorting from 8,000 to 9,000 an hour.
Overflow cost after the fix (AED millions):(200,000 - 9,000 × 20) × 90 × 5 ÷ 1,000,000 = 94. Payback of the cheap fix
AED 2 million against AED 9 million saved a year, in months.
Payback of the fix (months):2 ÷ (18 - 9) × 12 = 2.675. The sorter after the fix
It adds 6,000 an hour, which removes the remaining AED 9 million of overflow and saves AED 4 million a year of manual sorting outside the peak. It costs AED 3 million a year to run.
Net saving of the sorter (AED millions a year):9 + 4 - 3 = 106. Payback of the sorter
AED 40 million divided by 10 million a year.
Payback of the sorter (years):40 ÷ (9 + 4 - 3) = 47. Downside: peak of 175,000 a day
After the cheap fix the hub handles 180,000, so there is no overflow left for the sorter to remove; only the AED 4 million labour saving is left, minus AED 3 million to run.
Payback of the sorter in the downside (years):40 ÷ (max(0; 175,000 - 9,000 × 20) × 90 × 5 ÷ 1,000,000 + 4 - 3) = 408. The next limit
With the fix and the sorter, sorting reaches 15,000 an hour, and loading becomes the slowest step.
Hub capacity with the sorter (parcels a day):min(12,000; 9,000 + 6,000; 11,000) × 20 = 220,000
What the exhibit shows
Sorting is the bottleneck at 160,000 a day, 40,000 short of peak demand.
The recommendation
Do the cheap fix now, and decide on the sorter only when volume justifies it. Cutting jams on the manual sorting lines costs AED 2 million, halves the overflow bill from AED 18 million to 9 million a year, and pays back in under three months. The sorter would then pay back in about 4 years if peak demand stays at 200,000 a day, but if peak volume settles at 175,000 it would take about 40 years, because the fixed lines already cope. The main risk is volume, so set a signpost: order the sorter once peak days pass 180,000 parcels. When it comes, loading vans becomes the next limit at 220,000 a day, so plan that step too.
A strong candidate
Found sorting as the bottleneck from the table, put a money value on the problem (AED 18 million a year), fixed the cheapest thing first, then judged the sorter on payback and on a downside, and named the next bottleneck.
A weak candidate
Calculated the sorter's payback at the planned volume and said yes, without checking whether a cheaper fix could close most of the gap or what happens if volume is lower.
The interviewer asks: "So, should they buy the sorter?"
An opinion with no numbers
"Yes. The sorter adds a lot of capacity and automation is the future, so it will pay back over time."
Answer first, with numbers
"Not yet. Fixing jams on the current lines costs AED 2 million and halves the overflow bill from 18 to 9 million a year. After that, the sorter pays back in about 4 years at today's peak, but in about 40 years if peak volume is 175,000 a day. So I would fix the lines now and order the sorter once peak days pass 180,000 parcels."
Why the stronger answer wins: The strong answer leads with the decision, gives the numbers that drive it, tests a worse future, and names the signal that would change the answer. The weak one gives no numbers and no risk.
What to say at the end of an operations or cost case
- The decision, in one sentence: "Fix X first, then do Y when Z happens."
- The two or three numbers behind it: output gained, money saved, payback.
- The main risk, sized: what the answer becomes in the downside.
- The next step and the signpost that would change the plan.
- People and quality: who is affected, and what you would protect.
Jumping to the expensive answer (a new machine, a new plant) before checking the bottleneck and the cheap fixes. Giving a payback at the planned volume only. Cutting cost in a way that damages what customers pay for, such as making them wait. Forgetting that fixing one bottleneck moves the limit to another step. Leaving people out of a cost answer.
A client wants a new production line to meet demand. What should you check first?
A cost-saving machine pays back in 3 years at the planned volume. What is the best next question?
After you fix the bottleneck, what do you say next?
Logistics is operations in its purest form: capacity, utilization, peaks and cost per parcel. The logistics brief explains how the industry makes money and what it measures.
Read the logistics and shipping briefSources for this lesson (1)
- Recognized public explanations of case-interview concepts and terms
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