Deloitte Technology Case Interview: Structure an Architecture and Implementation Recommendation

A Deloitte technology case interview is preparation for a recommendation, not just an architecture diagram. Start with the business workflow and the constraint that cannot fail, compare a small set of technology options, then explain how the organization can implement your choice without losing control of data or operations.

This article focuses on technology-consulting case preparation. It does not describe a universal Deloitte interview sequence or replace a software-engineering coding guide. The worked case is original practice, not a leaked assessment. Start with Legacy Payroll System Migration Plan to test whether you can connect a migration design to a business-critical close process.

What Deloitte's current practice material actually supports

Deloitte's official US Consultative Offerings campus and early-careers page provides case-preparation context. Its current Case Prep Tool includes an Architecture Strategy case under undergraduate Tech Transformation and Enterprise Tech Strategy. That supports practicing this kind of reasoning; it does not establish that every Deloitte applicant receives the same exercise.

The official Architecture Strategy: Federal Finance Agency scenario connects fragmented legacy applications, information handoffs and operational constraints with enterprise architecture and implementation planning. Notice the combination: a technology recommendation must work for the people and processes that depend on it.

The tool describes itself as practice rather than an assessment and gives a completion estimate. Do not convert that estimate into your interview's timer. We did not establish two independent, same-cycle completed candidate reports for this exact technology-case route. Accordingly, this guide makes no claims about mandatory group work, question counts or a fixed hiring rubric. Confirm your role, country and invitation format before choosing a rehearsal.

Open with the decision the client needs

Consider this fictional case: a regional equipment-service company has separate dispatch, repair and warranty applications. Staff repeatedly re-enter asset information. Warranty claims occasionally contain conflicting serial numbers, and finance must complete month-end settlement without interruption. The technology team already spends most of its time maintaining the existing applications.

The request is: recommend an architecture and an implementation approach that reduces duplicate work while protecting warranty settlement. There is no prescribed cloud provider or deadline. Do not invent either to make the case easier.

A useful opening is:

I would first confirm which workflow causes the largest avoidable delay and which records must remain authoritative for warranty close. Then I would compare a workflow layer, a staged shared case platform, and full replacement. My recommendation would include data ownership, operational readiness and a decision about what not to migrate first.

That opening establishes an analytical path without declaring the answer prematurely. Ask whether “duplicate work” means repeated entry, repeated investigation or repeated approval. A single interface may solve the first problem while leaving the other two untouched.

Also clarify success. Fewer screens is an output. Less re-entry per eligible service case is a process result. Correct warranty settlement and faster customer resolution are business outcomes. You need a baseline and consistent populations before claiming that one causes another.

Build a business-to-architecture evidence map

Organize your notes around the decision, not a list of technologies. For each observed problem, name a proposed architectural response and the evidence needed to justify it.

Business constraint	Architecture implication and evidence to request
Asset identifiers disagree across applications	Establish a canonical asset identity and explicit mapping; inspect collisions, reused serials and unresolved records.
Staff re-enter the same repair details	Reuse a shared case record or supported integration; measure where duplication occurs before redesigning the whole workflow.
Warranty close cannot stop	Preserve the settlement system's authority initially; verify compatible exports, reconciliation and recovery procedures.
Maintenance capacity is limited	Prefer a small operational surface initially; estimate integration support, vendor dependencies and ownership, not just build effort.
Different branches work differently	Identify genuine policy differences versus avoidable local workarounds; pilot a representative workflow rather than the easiest branch alone.

An interviewer may supply incomplete data. State what you would investigate and which recommendation remains provisional. For example, identity conflicts could come from inconsistent formatting, duplicate assets or incorrect human matching. Those causes require different fixes. A new database does not resolve uncertainty about which physical asset a record represents.

Avoid assuming that every legacy system is unreliable. An old warranty ledger may be well controlled while the surrounding handoffs are slow. Preserve the valuable control, then reduce friction around it.

Compare three credible options

The first option is a workflow layer over existing applications. It can present staff with one coordinated task flow while the original systems retain their data responsibilities. It may reduce re-entry quickly, but adapters, synchronization and exception handling become continuing obligations. A polished interface can hide unresolved ownership conflicts.

The second option is a shared service-case platform introduced in stages. It owns case status and common service information while dispatch and warranty retain carefully defined boundaries. This offers a clearer long-term workflow, but requires a trustworthy asset map and explicit integration contracts. It is not automatically a collection of microservices.

The third option is full replacement. It might remove more legacy maintenance eventually, but combines workflow change, data conversion, settlement risk and staff retraining. Unless the case establishes a compelling requirement or an untenable current system, its larger transition risk is difficult to defend as the first move.

For the stated constraints, a reasonable provisional recommendation is the staged shared platform. Keep warranty settlement authoritative during the first wave, introduce common case tracking for a bounded workflow, and reconcile data before expanding. This is a recommendation based on the fictional facts, not a preferred Deloitte answer.

Explain why the alternatives lost. The wrapper is a useful interim choice if funding or delivery capacity is much smaller than expected. Full replacement becomes more plausible if the warranty application cannot satisfy a confirmed control requirement and has no viable upgrade path. Good case answers identify the facts that would reverse the decision.

Draw responsibilities before deployment components

Your diagram should make data ownership legible. Put the shared case platform between staff workflow and the existing applications, but label what each system owns. A connector is not a new source of truth simply because data passes through it.

For the first wave, dispatch owns scheduling, the service platform owns the repair case, and warranty owns settlement decisions. The asset mapping service supplies cross-system references with a visible unresolved state. Unmatched records enter an exception queue instead of being silently merged.

Walk through one service case. A dispatcher selects an asset, a technician records a repair, and warranty receives the relevant evidence. Then trace an exception: the serial number points to two assets. Which step stops, who resolves it, and what can continue safely? This reveals more practical judgment than naming a message broker.

Discuss access in business terms as well. A technician may need repair history without the ability to approve a warranty payment. Finance may need reconciliation exports without broad administrative privileges. Request the organization's actual policy; do not claim that one generic role model satisfies its obligations.

Only then discuss deployment, integration frequency and storage. Synchronous lookup may be appropriate for identity confirmation; settlement exports may be batch-oriented. The choice depends on workflow tolerances and supported interfaces, not an assumption that real time is always better.

Make implementation readiness observable

A migration plan needs gates that authorize progress. “Pilot, launch, monitor” is too vague unless you can say what passes a gate and who can stop it.

For this practice case, use the following readiness ledger. These are proposed controls to discuss, not measured results or universal threshold requirements.

• Begin shadow reads: Asset mappings are reviewed; access is appropriate; the old systems remain authoritative and no operational writes are redirected.
• Introduce one repair workflow: Staff can complete ordinary and exception cases; required fields and integration failures are visible; support ownership is assigned.
• Feed warranty evidence: Record counts and business totals reconcile over agreed cycles; discrepancies have named owners and cannot disappear into aggregate averages.
• Authorize a branch cutover: Operations and finance accept the evidence; recovery has been rehearsed; the branch has training, support and a clear write-authority boundary.
• Expand the next wave: Pilot evidence remains acceptable during close and exceptions; capacity is available for another branch, not merely for the initial launch.

Reconciliation should include meaning, not only row counts. Ten thousand copied rows can still have incorrect claim amounts, invalid asset references or missing attachments. Choose checks that correspond to the business failure you are trying to prevent.

Recovery is also more than switching the interface back. Once the new platform accepts writes, the old application may lack those changes. Explain how new records are retained, reconciled and replayed or manually resolved. If that path is untested, narrow the wave or postpone cutover. Do not promise zero data loss from a feature flag alone.

Defend the recommendation when constraints change

Suppose the interviewer says the maintenance team has only half the expected availability. Reduce concurrent change before cutting validation. Keep the common case platform's first workflow small, defer nonessential reports, and consider the wrapper as an interim step if it genuinely lowers ongoing support demands.

If finance refuses a cutover near month-end, move the operational wave or retain the settlement boundary longer. An architecture that requires stakeholders to abandon their critical process is not yet an implementable recommendation.

If a branch's identity conflicts are unusually severe, do not exclude it forever and declare the pilot representative. Treat that branch as a separate risk cohort. Investigate its records and determine what must be resolved before expansion. Otherwise, the easiest pilot can produce misleading confidence.

Finish with a compact client recommendation:

I recommend a staged shared case platform, retaining the warranty system as settlement authority initially. It addresses duplicate service work without combining every operational risk into one cutover. The first commitment is asset mapping and one repair workflow. Expansion requires business reconciliation, named support ownership and rehearsed recovery. If mapping quality or maintenance capacity is inadequate, I would reduce the wave or use a narrower interim integration.

That answer includes a choice, rationale, scope, risk and reversal condition. It does not require a memorized consulting acronym.

Practice the parts that make the recommendation defensible

Question	How to use it for this technology case
Legacy Payroll System Migration Plan	Preserve a business-critical close process; explain parallel reconciliation and cutover authority.
Choose Between a Monolith, Microservices, and a Modular Architecture	Compare operating complexity and ownership rather than equating more services with progress.
Migrate a Continuously Used Database	Separate copying records from preserving compatible reads and ongoing writes.
Own Production Incidents and Validate Large Pipeline Migrations	Design evidence that detects missing output without checking every task manually.
Design a Database Migration Service with Replication and Bottleneck Analysis	Connect replication, validation and capacity to a cutover decision.

Rehearse the equipment-service case once without choosing a vendor. Ask a partner to change one constraint after your recommendation. The useful diagnostic is whether your reasoning changes coherently, not whether you keep the same diagram.

Return to Legacy Payroll System Migration Plan and write the exact evidence that would make you delay launch. If you can defend both the architecture and the decision not to proceed yet, your preparation is closer to the task Deloitte's public technology practice material illustrates.

Sources and Further Reading

• Deloitte US: Consultative Offerings campus and early careers
• Deloitte: Case Prep Tool
• Deloitte: Architecture Strategy — Federal Finance Agency

Research checked October 6, 2026. Official practice material is not a guarantee of your interview format; the equipment-service case and proposed controls are original preparation examples.