How do I conduct technical due diligence on a codebase before acquiring a startup?

What Technical Due Diligence Actually Covers

Financial and legal due diligence tells you what a startup owns. Technical due diligence tells you what it will cost you to maintain, scale, or rebuild what you're buying. Skipping it — or treating it as a checkbox — is one of the most common and expensive mistakes acquirers make.

The Core Review Areas

1. Architecture and System Design

• Is the system modular or a tightly coupled monolith that's hard to change?
• Are there clear separation-of-concerns boundaries (frontend, backend, data layer)?
• How does the system handle load? Are there known bottlenecks?
• Is there a plan — or a problem — with scaling beyond current traffic?

2. Code Quality and Test Coverage

• Run static analysis tools (SonarQube, ESLint, Pylint, etc.) and review the output honestly.
• Check unit, integration, and end-to-end test coverage. Low coverage is a flag; zero coverage is a red flag.
• Look at commit history for patterns: frequency, message quality, who contributes, and what breaks repeatedly.

3. Security Posture

• Are dependencies up to date? Run a Software Composition Analysis (SCA) tool to surface known CVEs.
• Check for hardcoded secrets, exposed API keys, or misconfigured environment variables in version history.
• Review authentication, authorization logic, and data encryption at rest and in transit.

4. Infrastructure and DevOps

• Is the infrastructure version-controlled (Terraform, Pulumi) or manually configured?
• What does the CI/CD pipeline look like? Are deployments automated and repeatable?
• Understand hosting costs and vendor concentration — heavy lock-in to one cloud or proprietary service is a risk.

5. Technical Debt and Documentation

• Estimate the ratio of feature code to workaround code. Every system has debt; the question is whether it's managed or accumulated.
• Is there a README, API documentation, architecture diagram, or runbook? Their absence means the knowledge lives only in people's heads — people who may leave.

How to Structure the Process

1. Request a code repository access under NDA before any financial commitments.
2. Run automated scans first (dependency audit, SAST, coverage report) to get objective baselines.
3. Conduct developer interviews — ask the engineering team to walk you through a recent feature and a recent incident.
4. Produce a written findings report with severity ratings: critical (deal-breaker or significant renegotiation), major (remediation budget needed), minor (normal ongoing maintenance).

Using the Findings

A technical audit doesn't have to kill a deal — it should inform price, integration timeline, and post-acquisition remediation planning. Critical findings like exposed customer data or unlicensed third-party code warrant renegotiation or escrow conditions. Major technical debt should be quantified as estimated engineering effort and factored into your offer.

If you don't have an internal engineering team capable of doing this objectively, third-party firms can run the audit. CodeNicely, for example, conducts codebase audits for acquirers and investors — independently of whether they'll build anything afterward.