You cannot patch your way out of a fundamentally broken architecture. If your microservices trust each other implicitly without mutual TLS, or if your database uses a single shared root credential across all application clusters, running a penetration test is a waste of money. The pentester will immediately exploit the design flaw and hand you a report full of critical findings that require a total system rewrite to fix.
This is where an Architecture Review saves engineering cycles. Before you write the code, or before you deploy a massive refactor to production, we sit down with your engineering leadership. We map the trust boundaries. We find the logical flaws on the whiteboard before they become CVEs in your production environment.
What an architecture review actually covers
The review follows critical product flows across four connected layers. It uses system diagrams, infrastructure configuration files (like Terraform or Kubernetes manifests), API contracts, short code samples, and intense interviews with the engineers who actually own the system. A full line-by-line source code review sits outside this scope; we are looking at the skeleton, not the skin.
Authentication and authorisation flows
We map the entire lifecycle of a user identity: registration, login, MFA enforcement, account recovery, session renewal, logout, service identity, and privileged admin access. We then locate the specific enforcement point that owns role and object decisions. The design passes when each sensitive action has one clear server-side authorization path and one accountable owner. If your frontend React application determines whether a user is an admin by checking a boolean flag in local storage, your architecture fails immediately.
Data flows and storage
We trace sensitive data (PII, PANs, BVNs) from initial collection at the mobile client, through the WAF, into the APIs, across message queues (Kafka/RabbitMQ), down into the databases, and out into logs, analytics, support tools, and third-party vendors. Each data type needs a defined purpose, a distinct owner, a strict access rule, a retention rule, and a cryptographic deletion path. We check if your database backups are encrypted at rest and if your development environments are pulling unmasked production data.
API design and integration patterns
We review object ownership, request and response data, idempotency, rate controls, webhook verification, and multi-step transaction state. The design must define exactly what happens after a timeout, a duplicate message, a partial database failure, an automatic retry, a financial reversal, or a provider mismatch. If a payment webhook from Paystack or Flutterwave fails to include a cryptographic signature check in your API spec, attackers will forge successful payments.
Infrastructure and deployment
We review cloud boundaries in AWS, Azure, or GCP. We check service identity (IAM roles), secrets management (HashiCorp Vault or AWS Secrets Manager), deployment access (CI/CD pipeline permissions), VPC environment isolation, immutable backups, and centralized security logs. Each privileged path needs a named owner, least-privilege access, automated credential rotation or revocation, and immutable evidence of sensitive infrastructure changes.
Reviewing the CI/CD Threat Landscape
An architecture review is incomplete if it only looks at the production environment. We meticulously trace the path your code takes from a developer's laptop to the live server. We audit your GitHub Actions, GitLab CI, or Jenkins pipelines. If a junior developer's compromised GitHub account can merge code directly into the `main` branch without a mandatory secondary review, your perimeter security is irrelevant.
We check for hardcoded secrets in the repository history. We verify if your build runners possess excessive IAM permissions that allow them to modify production infrastructure outside of their defined deployment scope. A compromised build pipeline is the most devastating supply chain attack a fintech can face, as it allows attackers to quietly backdoor the compiled application before it even reaches the penetration testing phase.
Detecting Vendor Liability Chains
Modern fintech architectures are highly composable, relying on dozens of third-party vendors for KYC (SmileID, Dojah), core banking (Appzone, Woodcore), card issuing, and email delivery. We map the liability chain across these integrations.
If a vendor experiences an outage, does your system degrade gracefully, or does the entire payment flow crash? If a vendor's API is breached, what data of yours is exposed? We review the API contracts to ensure you are only sending the absolute minimum required PII to third parties. We also check your webhook verification logic to guarantee that attackers cannot spoof a vendor's callback and artificially inflate a user's wallet balance.
How it differs from a penetration test
A penetration test shows whether the running, compiled system can be exploited within an agreed scope right now. An architecture review checks whether the fundamental design puts controls in the right place to begin with.
Use the architecture review before major implementation work. Use a penetration test on the deployed product. Run both when you need design guidance to build the v2 platform and hard test results from the live v1 system. An architecture review prevents vulnerabilities; a penetration test discovers the ones that slipped through.
Every recommendation needs a testable result
A recommendation must name the failed trust rule, the affected flow, the target design, the owner, the priority, and the completion check. A generic "Improve access control" fails this rule. "Move transfer authorization into the shared policy service and test customer, support, and admin roles against every transfer action before compiling" passes it. We give you actionable engineering directives.
When to get an architecture review
Before a major launch or pivot
Review the design before the release path freezes. Focus on identity, money movement, customer data, privileged tools, third parties, and failure handling. Finding a fatal flaw in your authentication state machine two weeks before launch will delay your product by months. Finding it during the design sprint costs nothing. See our guide on security audits before launch.
Before a customer or due diligence review
Enterprise clients, partner banks, and venture capital firms will scrutinize your platform. Use the review to confidently answer design questions about system boundaries, data flows, roles, vendors, and open risks. External readers may still require a penetration test or SOC 2 report, but a verified architecture review demonstrates engineering maturity. Share a limited summary of our findings and keep the sensitive threat models inside the approved review group.
After a critical incident
Start with incident containment and evidence preservation. Review the architecture only after the incident response team identifies the failed controls and affected paths. The review then searches for the exact same trust rule failure across all other connected systems. If one microservice failed to validate a JWT signature, we will find the five other microservices written by the same team that share the same flaw. See the after a breach guide.
Want to know if your architecture needs a review before your next pentest?
Discuss an Architecture ReviewWhat you receive
You receive an agreed scope document, reviewed and corrected system diagrams, trust-boundary findings, a list of affected flows, a prioritized risk order, target controls, engineering owners, and pass conditions for each item. The report also lists the systems and business questions that fell outside the review scope, ensuring absolute clarity on residual risk.
To prepare, you must provide a current architecture diagram, a data-flow diagram, an RBAC roles matrix, key API Swagger contracts, the deployment model, a third-party vendor list, and documentation for the paths that change money, identity, access, or customer data. You must assign one senior engineering owner who can answer technical design questions and confirm the final diagrams during our whiteboard sessions.
Related reading
Blog: How a Simpa Labs pentest works · Zero trust architecture for fintechs · Microservices security
Guides: Security before fundraising · OWASP for fintech · Security checklist
Services: Architecture review · Penetration testing · API security