50 AWS Migrations Reveal 7 Costly Mistakes Teams Keep Repeating

A cloud engineer with over 50 AWS migration projects spanning startups to mid-sized enterprises has identified recurring pitfalls that derail timelines and inflate costs. Most teams skip the critical step of classifying workloads using AWS's seven migration strategies, defaulting to lift-and-shift even for applications that should be retired or replaced. Hidden networking costs — including cross-AZ data transfer, NAT Gateway fees, and internet egress — routinely push monthly bills thousands of dollars above estimates. Security shortcuts taken during migration, such as overly permissive IAM policies and unencrypted databases, are rarely fixed afterward and cost three to five times more to remediate later. The engineer recommends establishing security baselines, measuring real traffic costs during proof-of-concept phases, and spending several days on workload classification before any infrastructure is touched.