Why a post-migration AWS architecture audit is essential After a migration to AWS, many organizations discover in production gaps between the deployed infrastructure and cloud best practices, or between the actual architecture and the business objectives defined during the planning phase. These gaps only become visible a few weeks or months after go-live, when real workloads expose weaknesses in scalability, when costs turn out higher than projected, or when the promised resilience fails to withstand a first outage. A post-migration AWS architecture audit comes in at this critical moment. It provides a structured diagnostic of what works, what deviates from acceptable norms, and the actions to prioritize in order to align the infrastructure with the stated objectives. Unlike a superficial technical audit that just produces a list of problems, a post-migration architecture audit is grounded in the initial business intent, that is, the strategy and business priorities the organization had at the start of the project. This makes it possible to distinguish what is truly urgent (a failure to meet priority objectives) from what is a matter of long-term optimization. For a scale-up or a mid-sized company coming out of a major migration with a small, overstretched platform team, this audit plays the role of a clear map that prevents running in every direction at once. ## The five pillars to evaluate in a post-migration architecture audit A post-migration AWS architecture audit cannot be chaotic or focused on a single technical area. It must follow a structured framework covering five interdependent domains, each critical to the long-term success of the infrastructure in production. The first pillar is alignment with business objectives. The audit verifies that each architectural decision made during the migration (choice of AWS services, resource sizing, high-availability strategy) still answers the business priorities stated up front. For example, if the objective was a 40% reduction in the infrastructure bill, the audit will measure whether this saving is actually achieved or whether hidden overspend (data transfer, poorly sized services, non-optimized instances) has cut the saving to 15%. If the priority was to support 3x load growth over 12 months, the audit will assess whether the current architecture can support that growth without a major redesign. The second pillar is compliance with AWS best practices, as defined by AWS's own Well-Architected Framework. This includes operational excellence (centralized logs, monitoring in place, documented runbooks), security (granular IAM, encryption of data in transit and at rest, network segmentation, compliance with the applicable standards), reliability (failover mechanisms, retry policies, failure handling), performance efficiency (configurations optimized for the real workload, not defaults), and cost optimization (identifying oversized resources, rightsizing, relevant reservations). The third pillar is the quality of the architecture itself: consistency of the patterns used, absence of unnecessary coupling between services, modularity, scalability, and maintainability. An architecture audit often reveals decisions made under pressure during the migration that create technical debt (for example, a containerized monolith on EC2 instead of a decoupled architecture with managed services). The fourth pillar is performance and economics under real conditions. The audit analyzes the runtime metrics during the first weeks or months of production: application response times, actual usage of the allocated resources, effective costs per service, behavior during load peaks, and the latency observed on critical operations. This makes it possible to see whether the sizing was realistic or whether it needs to be adjusted up or down. The fifth pillar is operational readiness: does the platform team responsible for day-to-day maintenance have the tools, processes, and skills to operate the infrastructure under stable production conditions? Is there a backup and disaster recovery strategy in place and tested? Are the runbooks for critical incidents documented and accessible? Do alerts reach the right teams at the right time? Each of these five pillars generates a distinct diagnostic, but it is their interactions that reveal the real problems. For example, excellent compliance with AWS best practices does not compensate for a major gap against the initial business objectives; conversely, an architecture that meets the business objectives but lacks security standards creates a regulatory or breach risk. ## How to structure the execution of a post-migration architecture audit An effective post-migration architecture audit is not limited to interviews with the architects and a review of code or cloud diagrams. It is a methodical investigation that combines several types of data and observations, each validating or invalidating the others. The first step is to establish a baseline of what the architecture should be according to the intentions stated before the migration. This means rereading the initial migration strategy, the business requirements, the target RTO and RPO, the compliance constraints, and the cost priorities. If these documents exist, they form the guide for what the audit must validate. If these documents are missing, that is already a problem the audit must flag: a migration without written, measurable objectives is doomed to fail on business alignment. The second step is the exhaustive inventory of what actually exists in production. This includes an automated scan of all AWS services in use (via AWS Config, Systems Manager Inventory, or a third-party tool like CloudMapper or Cloudcraft), a manual mapping of the network architecture and data flows, an extraction of the critical configurations (IAM policies, security groups, VPC peering, routing, NLB/ALB rules), and a measurement of the performance observed over a representative period (ideally 2 to 4 weeks that include a load peak). All of this must be documented in a unified diagram to avoid misunderstandings. The third step is the qualitative evaluation against the five pillars. For each domain (business objectives, AWS best practices, architecture quality, performance, operations), you compare the theoretical baseline (what should be) against the observed reality (what is). Each divergence is classified by severity (critical, high, medium, low) according to its impact on stability, security, costs, or the team's future ability to operate and evolve the infrastructure. The fourth step is the formulation of prioritized recommendations. The audit must not generate a list of 60 items to handle. It must identify the 5 to 10 most impactful actions which, if executed within 3 to 6 months, would rectify the major gaps. This means noting the dependencies between actions (some must be done before others), the estimated effort of each action, and the foreseeable impact in terms of cost saved, risk reduced, or capability added. The fifth step is the production of an executive report that summarizes the key findings, followed by a detailed action plan that specifies for each recommendation: the steps to follow, the responsible team, the dependency on other actions, the estimated effort (in engineer-days), the budget if additional licenses or services are needed, and the success indicators that will prove the action solved the identified problem. For an overstretched mid-sized company or scale-up, this plan should be delivered at a fixed price announced in advance and in days rather than in quarters, so it can be integrated without friction into its delivery calendar. ## Common gaps found during post-migration audits After dozens of post-migration architecture audits, certain gaps come up regularly. Identifying them in advance helps avoid letting them settle in permanently in production. The most frequent gap concerns costs. A migration is often planned with a global cost assumption that turns out optimistic once in production. Recurring causes include: EC2 instances oversized to anticipate a peak load that never happens, EBS volumes not deleted after load tests, forgotten snapshots that pile up, or an unoptimized data transfer strategy between AWS regions. An audit generally reveals 20 to 35% of possible savings just by cleaning up and rightsizing the existing sizing, without any architectural overhaul. The second gap concerns security and compliance. During the migration, under time-to-market pressure, certain security decisions are deferred. Typical examples: security groups left open (0.0.0.0/0) on sensitive ports "temporarily," encryption of data in transit enabled selectively rather than systematically, or IAM still very permissive on developer roles. A post-migration audit often finds that these temporary measures have become permanent and are widening an ever-growing gap with the company's security policies. The third gap is architectural and concerns the services used. Many migrations simply drop the existing workloads onto EC2 or ECS without refactoring to take advantage of AWS managed services. This "lift-and-shift" approach is valid for a fast migration, but it creates technical debt: the team has to manage servers when AWS offers RDS managed for databases, ElastiCache for caching, SQS/SNS for queues, Lambda for scheduled tasks, and so on. An audit often reveals that it is possible to remove 30 to 50% of the management surface (by replacing self-managed with managed) with no additional cost and no reduction in performance. The fourth gap is operational: logs, monitoring, and alerts are not configured consistently. CloudWatch may be enabled on some services but not others, application logs go to CloudWatch Logs, VPC Flow logs go to S3, and there is no centralized dashboard giving a holistic view of the system's health. When an incident occurs, the team has to manually assemble information from several sources, which slows the diagnosis. The fifth gap concerns resilience and business continuity. During the migration, a choice had to be made between a multi-AZ deployment (more expensive, more complex) and a single-AZ deployment (simpler, cheaper). Many organizations choose single-AZ "temporarily" with the promise of moving to multi-AZ "in six months." The audit often reveals that no RTO/RPO has been measured under real conditions and that failover capability has never been tested. An outage in one AZ would have a far greater impact than expected. The sixth gap, less visible but crucial for an overstretched platform team, is the absence of documentation and runbooks. The architecture may be technically good, but not a single person knows how it really works, what to do in the event of specific alerts, or how to provision a new resource correctly. This creates a turnover risk: if a key person leaves, the organization loses the tacit understanding of the infrastructure at the same time. Each of these gaps can be discovered and quantified during a post-migration audit, and each generates one or more recommendations that can be integrated into a pragmatic, costed action plan. ## Connection with technical debt remediation and post-migration cleanup A post-migration AWS architecture audit does not stop at identifying the gaps. It must also clarify how these gaps feed into the next steps of the transformation cycle. Many of the architectural gaps discovered during the audit generate what is called technical debt: temporary compromises, suboptimal patterns, or dependencies that complicate future maintenance and evolution. Remediating this technical debt is different from post-migration cleanup. Post-migration cleanup (removing test resources, orphaned EBS volumes, stopped but not deleted instances) is tactical hygiene work that can be done quickly. Technical debt remediation is strategic work that requires reworking the architecture: refactoring a monolith to decouple it, replacing self-managed with managed, putting a real multi-AZ strategy in place, or migrating an oversized database to a sharded architecture. The post-migration audit produces two distinct lists: a cleanup list (short term, inexpensive, low risk) and an architectural remediation list (medium to long term, more expensive, requiring coordination). These lists must be prioritized together to create an infrastructure consolidation plan that reconciles the three objectives: speed of stabilization in the short term, cost control in the medium term, and durable architectural quality in the long term. It is in this connection that the audit reveals its full value: it allows the scale-up or mid-sized company to say yes to certain actions (cleanup and quick optimizations that deliver 60% of the benefits) and to strategically plan others (technical debt remediation that requires more effort but transforms the infrastructure). Without a clear audit, these decisions are made case by case, often in reaction to incidents rather than in prevention. ## Metrics and success indicators after a post-migration audit For a post-migration AWS architecture audit to have a real and measurable impact, it must define clear success indicators that make it possible to track progress and validate that the recommendations have achieved their goal. The success indicators must be defined for each pillar evaluated. On business alignment, the indicators can be: cost gap relative to the initial budget (targeted at less than 10% gap), scaling capability up to 3x the initial load without incident, or RTO/RPO measured and compliant with the stated objectives. On compliance with AWS best practices, the indicators can be: Well-Architected Framework score improved by X points, compliance with internal security policies at 100%, or monitoring coverage raised from 40% to 95% of critical services. On architectural quality, the indicators can be: reduction in operational complexity (number of hours per month spent handling incidents, cut by 50%), or runbook coverage raised from 20% to 100% of critical incident scenarios. On performance and costs, the indicators can be: AWS bill reduced by 25%, or P99 response time cut from 500ms to 200ms. On operational readiness, the indicators can be: infrastructure availability rate raised from 99.0% to 99.5%, or onboarding time for a new engineer on the platform cut from 4 weeks to 2 weeks thanks to documentation. Each of these indicators must be measurable, meaning the team has a clear baseline (state before the audit), a clear target (state after the actions), and a way to measure progress (dashboards, logs, tickets, quarterly audit cycles). Without these three elements, the action plan risks staying opaque about its real results. A good practice is to run a post-migration audit 6 to 8 weeks after go-live, because that is when the real load patterns emerge and the operations teams have enough command of the platform to identify the problems that are not immediately obvious. A second audit is often beneficial 6 months after go-live to assess the quality of execution of the recommendations and adjust the priorities according to the evolution of business needs.