AWS Application Migration Service (MGN)

AWS Application Migration Service (MGN) is Amazon's agent-based rehosting service: it continuously replicates on-premises, virtual, or cloud servers at the block level and converts them into native Amazon EC2 instances with a cutover window AWS documents in minutes rather than hours. It reached general availability in May 2021, superseding AWS Server Migration Service as the recommended lift-and-shift path onto AWS, and in June 2026 AWS rebranded it as AWS Transform MGN, folding it into the AWS Transform family of agentic migration tools while keeping the same replication engine underneath.

Architecturally, a lightweight Replication Agent on the source server streams block-level changes to a staging area in the target AWS account and Region, requiring no configuration change on the source environment. Before cutover, teams can launch non-production test instances from the replicated data and validate the migration without touching production. Work is organized through three configurable per-server templates — replication, launch, and post-launch — and servers group into applications and waves, so cutover, launch, and archival run in bulk across a large estate rather than server by server.

What MGN does not do matters as much as what it does. It is a rehost tool, not a modernization tool: it does not refactor application code, and it does not convert a database engine or schema, which is AWS Database Migration Service and the Schema Conversion Tool's job. AWS frames it as a fast first step toward modernization, with any replatforming or refactoring happening afterward once the workload already runs on EC2. The one partial exception is a small library of opt-in post-launch actions — Windows Server version upgrades, cross-Region disaster recovery configuration, and Windows MS-SQL BYOL-to-AWS-license conversion — which are narrow steps, not a general license remediation service.

On pricing, each source server gets 2,160 free hours (90 days of continuous replication) starting when the Replication Agent is installed, and AWS states most migrations complete inside that window; replication is billed hourly per server after it. The free tier covers only the MGN service charge, not the AWS infrastructure MGN provisions to do the work — EC2 and EBS costs for the replication staging servers, and for every test and cutover instance launched along the way, accrue from day one.

MGN fits when the goal is exiting a data center or a source cloud quickly with the smallest possible risk surface: no code changes, same OS, same application, different hardware underneath. It is the wrong tool when the actual goal is modernization — replatforming to managed services, decomposing a monolith, or converting a database engine — and it is the wrong tool for a buyer whose need is a delivery engagement rather than a specific AWS product. Inside AWS Transform it is the replication engine beneath a broader rehost workflow covering discovery, wave planning, and network migration, in either an agentic mode or the original self-directed console workflow; it is not a substitute for that surrounding planning work. Product-state claims here were verified against AWS documentation in August 2026.