Hire a legacy-systems integration engineer for the work of connecting systems whose behavior, documentation, or change process may be constrained. The role needs more than experience calling a modern API.
Define the systems, access limits, and operational consequences at a generalized level before recruiting.
Map the integration uncertainty
| Area | What the hire must establish |
|---|---|
| Interface | Available protocols, formats, and supported access paths |
| Meaning | How each system represents the same business concept |
| Reliability | Failure, timeout, retry, and duplicate behavior |
| Change | Who controls versions and maintenance windows |
| Migration | How old and new paths coexist or transition |
| Support | Who diagnoses failures after launch |
The difficulty may lie in organizational ownership as much as code. State who can answer questions about the existing system.
Distinguish discovery from implementation
If the interface is poorly understood, the role needs time to inspect behavior and verify assumptions. Do not present the job as straightforward delivery against a complete specification.
If the interface is stable and documented, prioritize dependable implementation and operation rather than overstating the need for reverse engineering.
Only use authorized access and supported investigation methods.
Assess with a fictional transaction
Describe a fictional order passed between a modern application and an older system. The older system times out without confirming whether it accepted the order.
Ask how the candidate would avoid duplicate effects, reconcile state, and communicate uncertainty. Explore what they would do if the system has no reliable status query.
A strong answer should explain limits and tradeoffs rather than promise exactly-once behavior without the necessary guarantees.
Review migration judgment
Ask how they would verify data mappings, test compatibility, stage a transition, and recover from a failed cutover. Include the operational teams who depend on the workflow.
Do not ask candidates to design a live customer migration as unpaid interview work.
Define the ongoing mandate
State whether the hire will maintain the integration, hand it to another team, or establish a reusable pattern. Clarify documentation, monitoring, and support responsibilities.
Use the backend ownership canvas and data quality assessment. Discuss an integration engineering search with Refery.