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Cloud · On-prem → Azure / AWS · Lesson 8 of 8

Interview: hybrid is a design, not an apology

Interviewers ask whether you will be hybrid forever or whether you have an exit. Both are designs. Weak answers reboot a VM. Strong answers name the landing zone, identity, network, control map, and rollback for pay-api — and they do not lift the DC this weekend.

Updated 2026-08-18·22 min read·L2 primary·Quiz at end

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The ticket

Twelve minutes. Whiteboard: dc01 10.20.30.10, fgt-hq 203.0.113.10, pay-api 10.20.30.40, Azure hub 10.40.0.0/16, AWS hub 10.50.0.0/16. They will ask if hybrid is a failure. It is not. An accidental hybrid with two password islands is.

Strong answer pattern

Name the decision (R, landing, identity, path, control, rollback) → name the object (MG, tunnel, A record, NSG vs Firewall) → name the proof (IKE list, nslookup, POST /v1/pay, Sentinel hit) → name the trap. Weak: “we will lift and then see.” Strong: “wave-1 is pay-api rehost into sub-spoke-app after Connect sync and vpn-azure; success is POST /v1/pay; on-prem stays read-only.”

Hero · whiteboard
Interview whiteboard of hybrid pay-api migration
If you cannot draw wave-1, you are not ready.
Lab data · dummy only

On-prem DC dc01 10.20.30.10 · FortiGate fgt-hq 203.0.113.10 · same Azure landing as the Azure series and same AWS landing as the AWS series. Wave-1 app pay-api today on VM 10.20.30.40.

Hybrid forever vs exit

Hybrid foreverExit
MeaningOn-prem stays a site. Cloud is another site.A program to empty the DC, last thing is identity/data.
This labValid — dc01 retain, SQL may stay, pay-api rehostValid — but not wave-1, and not this weekend
IdentityConnect / Cloud Sync staysCutover directory only after apps do not need Kerberos
NetworkVPN then maybe ER/DXSame, until the last subnet leaves
Failure modeTwo password islands, two writersDeleting on-prem before soak / before identity exit

Hybrid is the default for wave-1. Exit is a portfolio, not a cutover step.

What they score

Landing zone · identity · network · control map · rollback. If your answer skips those five, it is a feature dump.

16 questions

Q1 · Lift the DC this weekend?

PM wants every VM on 10.20.30.0/24 moved.

Strong
No. 6 Rs per app. Wave-1 is pay-api only. dc01 is retain.

Q2 · What is a landing zone?

They point at a subscription with one VM.

Strong
Identity + MG/OU + hub + logging before the first workload VM. That sub is dirty.

Q3 · Where does pay-api land?

Junior used his personal subscription.

Strong
sub-spoke-app / Workloads OU. Spoke 10.41.0.0/16 or app VPC 10.51.0.0/16. Not sub-hub, not a sandbox.

Q4 · New Entra passwords for everyone?

Cloud team sent welcome mail.

Strong
No. Hybrid identity first — Connect or Cloud Sync from dc01. That mail is a password island.

Q5 · Connect vs Cloud Sync?

One forest, no federation yet.

Strong
Cloud Sync is enough for this lab. Connect if you need PTA/federation/complex topology. Neither replaces dc01 in wave-1.

Q6 · AWS humans with access keys?

Someone created IAM users.

Strong
IAM Identity Center, sourced from Entra/AD. Keys for humans are a finding, not a design.

Q7 · ExpressRoute first?

Circuit is eight weeks out.

Strong
VPN now: fgt-hq 203.0.113.10 to Azure 203.0.113.50 and/or AWS 203.0.113.60. ER/DX later for volume/SLA.

Q8 · VPN up, app dead?

IKE green. Users still on the old box.

Strong
DNS. nslookup pay-api.techclick-lab.in against dc01. Conditional forwarder / Private DNS / Route 53 is the silent breaker.

Q9 · Overlapping CIDR?

Someone wants the spoke to be 10.20.30.0/24.

Strong
Refuse. IPsec cannot route that overlap. This lab already has 10.40/10.41 and 10.50/10.51.

Q10 · Lift or rebuild?

OS is supportable, app is a black box.

Strong
Azure Migrate or MGN lift. Rebuild if OS is rotting or the target is PaaS — as a separate program.

Q11 · IP + DNS + auth tonight?

Junior wants one big change.

Strong
No. One variable and a rollback. Test name first. Production A record last.

Q12 · NSG equals FortiGate?

Checklist says “NSG allow 443.”

Strong
No. NSG/SG is 5-tuple. Map IPS/WAF/logs to Azure Firewall+WAF+Sentinel or AWS NFW+WAF+Security Hub.

Q13 · Drop WAF because cloud is secure?

Budget slide.

Strong
Shared responsibility does not cover your HTTP app. Map the control or accept the risk in writing. Do not drop it silently.

Q14 · VM running — are we done?

Portal is green.

Strong
No. Success is POST /v1/pay on the name, logs on the cloud IP, one writer.

Q15 · Delete on-prem at flip?

License saving.

Strong
No. Read-only until soak ends. Rollback is DNS back to 10.20.30.40.

Q16 · Hybrid forever or exit?

The closer.

Strong
Hybrid is a design: dc01 retain, VPN, synced identity, one app at a time. Exit is a later program — identity and data last — not a weekend. Accidental hybrid (two passwords, two writers, no control map) is the failure.

Weak vs strong

WeakStrong
Lift everything / reboot the VM6 Rs, wave-1 = pay-api
We have a subscriptionMG/OU, hub 10.40 or 10.50, logs first
Cloud-only accountsConnect / Cloud Sync + IAM Identity Center
Wait for ExpressRouteVPN now, ER/DX later
NSG is the firewallControl map including IPS/WAF/SIEM
VM is runningPOST /v1/pay + rollback DNS

How to prove it

You are ready when

You can walk Q1, Q8, Q12, Q14, Q16 in 90 seconds each with dummy IPs and one proof command each (IKE list, nslookup, control-map row, curl POST, DNS revert).

Traps

Memorising “6 Rs” without a wave-1 sentence still fails. Hybrid forever is allowed. Two writers and two password islands are not.

Knowledge check

Judgment items. One best answer. Reasons send you back to the matching section.

Q1

Wave-1 answer if they say “move the DC”?

Correct: b. Q1.
Q2

Landing zone minimum?

Correct: a. Q2.
Q3

VPN up, users still on 10.20.30.40. Ask…

Correct: a. Q8.
Q4

NSG allow 443 replaces FortiGate?

Correct: b. Q12.
Q5

Cutover success proof?

Correct: b. Q14.
Q6

Hybrid forever is…

Correct: b. Q16.

On-prem to cloud migration class series: 6 Rs · Landing zone first · Identity first · VPN / ER / DX · Lift vs rebuild · Map controls · Cutover + rollback · Hybrid interview

Sources

Related: Azure landing zone · AWS Org / OU.