Technical Due Diligence: What Investors Check Before Writing a Check

A Series B SaaS company was three weeks from closing a €15 million round. The lead VC sent in a technical due diligence team — two senior engineers who spent five days auditing the codebase, infrastructure, and engineering processes. They found: zero automated tests, API keys hardcoded in the frontend JavaScript, a single-server deployment with no failover, and the entire database accessible without Row-Level Security. The investment was downgraded to €5 million with a mandatory €2 million earmark for engineering remediation. The founders lost 40% of their expected valuation because they treated code quality as optional.

Technical due diligence is no longer a formality. Stripe’s Developer Coefficient study — a large-scale survey of professional developers still cited as the benchmark reference on engineering time loss — found that developers spend an average of 17.3 hours of a 41.1-hour work week, roughly 42%, dealing with technical debt and bad code. That is not an abstract inefficiency; it is exactly the maintenance burden a buyer inherits the day the deal closes, and sophisticated investors now price it in before they sign. What a due diligence team finds determines whether you close at your asking price, close at a discount, or do not close at all.

CB Insights’ long-running analysis of VC-backed company shutdowns puts “no market need” and weak product-market fit at the top of the failure list — but among the startups that do find their market, execution risk buried in the codebase is precisely what a technical audit exists to surface before a term sheet becomes a wire transfer.

What Auditors Actually Look At

Technical due diligence teams typically evaluate seven areas, each weighted by how likely it is to kill the deal:

1. Code Quality and Architecture (High Impact)

Auditors clone your repository and start reading. They are looking for:

• Consistent code style — does the codebase look like it was written by one team with shared conventions, or by 15 freelancers who never talked to each other?
• Separation of concerns — is business logic cleanly separated from infrastructure code? Can they understand the data flow by reading the directory structure?
• Technical debt density — are there TODO comments from 2024 that were never addressed? Are there “temporary” workarounds that became permanent?
• Framework currency — are you running on supported, current versions of your frameworks, or are you two major versions behind with known vulnerabilities?

2. Test Coverage (Deal Breaker)

The presence or absence of automated tests is the single strongest signal of engineering discipline. Auditors run your test suite and check:

• Coverage percentage — 80%+ for business logic is the benchmark. Near-zero test coverage is consistently treated by technology M&A advisors as one of the findings most likely to trigger a valuation haircut, because it converts every future release into an unquantified risk.
• Test quality — are tests actually testing meaningful behaviour, or are they trivial assertions that inflate coverage numbers?
• CI integration — do tests run automatically on every pull request, or are they run manually (if at all)?
• Delivery performance against known benchmarks — DORA’s State of DevOps research (Google Cloud’s long-running study of software delivery performance, the basis for the “Accelerate” research programme) classifies engineering organisations into four performance tiers. Elite performers deploy on demand with lead times under a day, a change failure rate around 5%, and recovery from a failed deployment in under an hour. Low performers sit at a roughly 64% change failure rate and can take a month or longer to recover from an incident. A due diligence team that pulls your deployment logs is, in effect, checking which tier you fall into — and a startup clustered with “low performers” on these metrics faces harder valuation conversations regardless of what the pitch deck claims about engineering velocity.

3. Security Posture (Deal Breaker)

Auditors will specifically check for:

• Exposed API keys and secrets in source code or version history
• SQL injection and XSS vulnerabilities in user-facing endpoints
• Authentication and authorisation implementation
• Data encryption at rest and in transit
• Dependency vulnerabilities (unpatched CVEs)
• GDPR and data privacy compliance

Finding a single hardcoded production API key in a public repository is, in our experience advising founders through diligence, often enough on its own to reopen valuation negotiations — not because the fix is expensive, but because it signals that nobody on the team owns a secrets-management process, which auditors read as a proxy for how the rest of the codebase was built.

4. Infrastructure and Deployment (High Impact)

• Deployment automation — can you deploy to production with a single command, or does it require manual SSH access and prayer?
• Environment separation — do you have distinct development, staging, and production environments?
• Disaster recovery — automated backups, tested restoration procedures, defined RTO (Recovery Time Objective) and RPO (Recovery Point Objective)
• Monitoring and alerting — can you detect production issues before your customers do?

5. Scalability (Medium Impact)

• Can the application handle 10x the current traffic without a rewrite?
• Are there obvious performance bottlenecks (N+1 queries, missing database indexes, no caching)?
• Is the infrastructure horizontally scalable (can you add servers) or vertically limited (one big server that cannot grow)?

6. Documentation (Medium Impact)

• Architecture documentation that a new engineer can use to understand the system
• API documentation for any external-facing interfaces
• Runbooks for common operational procedures (deployment, rollback, incident response)
• Architecture Decision Records explaining why key technical choices were made

7. Team and Process (Medium Impact)

• Version control practices — meaningful commit messages, feature branches, code reviews
• Development process — sprint cadence, backlog management, definition of done
• Knowledge distribution — is all critical knowledge in one person’s head (bus factor of 1)?

The Pre-Due Diligence Checklist

If you are planning to raise a round or position for acquisition in the next 12 months, start preparing now. Here is the checklist:

The Red-Flag Severity Framework

Not every finding in a technical due diligence report carries the same weight, and founders who treat every item on the auditor’s list as equally urgent waste their remediation budget on the wrong fixes. Experienced diligence teams implicitly triage findings into four severity tiers — making that triage explicit lets you prioritise the same way the auditor will read your report.

The practical takeaway: a founder with four weeks before an audit should ignore Tier 4 entirely, treat Tier 3 as a checklist to clear, and focus disproportionate effort on anything that could plausibly be scored as Tier 1 or Tier 2 — those are the findings that move the number on the term sheet, not the ones that make the report longer.

Preparing With a Distributed Team

Preparing for technical due diligence is one of the highest-ROI activities a startup can undertake. At Manifera, our custom software development teams regularly help startups remediate technical debt and implement engineering best practices ahead of funding rounds.

Our Amsterdam-based architects conduct code quality assessments, while our Ho Chi Minh City engineers implement the fixes — a combination that delivers investor-ready code quality within 4-8 weeks at a fraction of the cost of European-only teams.

Get your codebase investor-ready — manifera.com/contact-us.

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