BCG · Technology / Operations · Intermediate · 25-35 min

Retire legacy systems and consolidate technology footprint

Retire legacy systems and consolidate technology footprint is an intermediate BCG technology / operations case interview that runs 25-35 min. Prioritize systems for retirement, estimate savings and risks, and create a phased decommissioning plan. A strong answer works through 5 phases: Legacy system inventory and dependency mapping; Business criticality and retirement sequencing; Migration and data consolidation strategy; Identified risks (operational disruption, talent); Cost savings and timeline.

Last updated 2026-09-05

The brief

A large retail bank operates 40+ legacy systems built on deprecated technology (COBOL, mainframe) that costs $200M annually to maintain. Business capabilities have been replicated in modern systems. Develop a legacy system retirement strategy.

How to approach it

  1. Legacy system inventory and dependency mapping
  2. Business criticality and retirement sequencing
  3. Migration and data consolidation strategy
  4. Identified risks (operational disruption, talent)
  5. Cost savings and timeline

What a strong answer does

  • Prioritize systems for retirement, estimate savings and risks, and create a phased decommissioning plan.
  • Retire 70% of systems over 5 years, starting with lowest-risk, lowest-revenue systems. Consolidate on 5 modern platform stacks. Expect 40-50% reduction in ops costs and increased agility.

Practice drills

  • Map dependencies between 40 legacy systems to identify safe retirement candidates.
  • Estimate savings from retiring 70% of systems over 5 years.
  • Design a phased decommissioning plan with go-live dates.
  • Identify skills and talent implications of modernization.

Why this case

Tests portfolio thinking, risk management, and ability to sequence a large multi-year transformation program.

Adapted from BCG Legacy Modernization case (official sample).

Cases are written in each firm's style, written and reviewed by working consultants; they are not the firms' own published cases.

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