• What Technical Due Diligence Actually Is

• What Investors Check

  • Architecture and Scalability

  • Code Quality and Technical Debt

  • Security and Compliance

  • Infrastructure and DevOps Maturity

  • Team and Knowledge Concentration

  • Product and Roadmap Alignment

• Common Red Flags That Delay or Condition Deals

• How Engineering Teams Should Prepare

  • Start with a Self-Audit

  • Get Your Infrastructure Documentation in Order

  • Address the Obvious Security Issues First

  • Reduce Knowledge Concentration

  • Prepare Your Team for the Interview Process

• When You Need External Help

• The Difference Between Passing and Sailing Through

• FAQs

Your fundraise is going well. The deck landed, the partner meeting exceeded expectations, and the term sheet conversation is moving. Then the investor says: "We'll need to run technical due diligence before we close."

For many founders, that sentence triggers a quiet panic. Not because the product is broken, but because nobody has formally audited it before. The codebase grew fast. Infrastructure decisions made sense at the time. The team knows where the bodies are buried — they just haven't written any of it down.

Technical due diligence is how investors verify that your engineering is as strong as your pitch suggests. Done well, it confirms your valuation and accelerates the close. Done poorly, it opens the door to renegotiation, conditions, or worse.

Here's what investors actually look at, what gets flagged, and how your engineering team can get ahead of it.

What Technical Due Diligence Actually Is

Technical due diligence is a structured review of your product, codebase, infrastructure, and engineering team. It's typically commissioned by the investor and carried out by an independent technical advisor or specialist firm.

Scope varies by stage. At Series A, investors want confidence that the product can scale. At Series B, they want evidence the engineering organisation can scale too. Pre-seed and seed deals sometimes skip formal technical due diligence entirely — but that's changing as investors become more technical.

The review usually runs two to four weeks, combining document review, codebase access, architecture interviews, and sometimes live demonstrations of the system under load.

What Investors Check

Architecture and Scalability

The first question is straightforward: can this product handle 10x the current load without a rewrite?

Investors look at how the system is structured — whether it's a monolith that will need breaking apart at scale, or whether there's a clear path to distributing the load. They check whether the architecture was designed with growth in mind, or built to ship fast and never revisited.

Data architecture gets scrutiny too. Where does the data live? How is it partitioned? What happens when the database becomes the bottleneck?

This isn't about penalising early-stage decisions. Investors understand that scale-ups make pragmatic choices. What they want to see is that you understand the limitations of your current architecture and have a credible plan to address them.

Code Quality and Technical Debt

Reviewers will look at the codebase directly — assessing test coverage, documentation, code consistency, and known vulnerabilities in dependencies.

High technical debt isn't automatically a deal-breaker. What matters is whether the team has visibility into it and a plan to manage it. A codebase with 40% test coverage and a documented debt backlog is a better signal than one with 80% coverage but no idea where the fragile parts are.

Common flags: large volumes of commented-out code, no version control discipline, missing or outdated API documentation, dependencies that haven't been updated in over a year.

Security and Compliance

Security is increasingly a first-order concern. Investors check for basic hygiene: secrets management, access controls, audit logging, and vulnerability scanning in the CI/CD pipeline.

If your product handles personal data, they'll look at GDPR compliance posture. If you're selling into enterprise, ISO 27001 or SOC 2 readiness may come up. A gap here doesn't kill a deal, but it often becomes a condition of closing.

Infrastructure and DevOps Maturity

How is your infrastructure managed? Is it documented? Could someone who's never seen it before understand how to deploy, roll back, and recover from an incident?

Investors look for infrastructure as code, meaningful monitoring and alerting, and a deployment process that doesn't depend on a specific engineer being online. They also check your incident history — not to penalise you for having incidents, but to see how you responded.

A well-documented post-incident review is a positive signal. It shows the team learns from failure rather than repeating it.

Team and Knowledge Concentration

This one catches founders off guard. Investors look at whether engineering knowledge is concentrated in one or two people. If your lead engineer left tomorrow, how long would it take the rest of the team to understand the system?

Bus factor is the informal term. If the honest answer is "we'd be in serious trouble," that's a risk investors will price into the deal.

They also look at hiring practices, onboarding documentation, and whether the team has the depth to execute the roadmap without immediately needing to hire five more engineers.

Product and Roadmap Alignment

Technical due diligence isn't purely about the code. Investors also check whether the engineering team and the product roadmap are actually aligned — whether technical priorities match business priorities, and whether the team is building the right things.

Sprint velocity, delivery consistency, and how the team handles scope changes all get examined. A team that ships predictably is more valuable than one that ships fast but erratically.

Common Red Flags That Delay or Condition Deals

• No automated testing, or test coverage below 20%

• Infrastructure managed manually with no documentation

• Security credentials stored in the codebase or in plain text

• No disaster recovery plan or untested backups

• A single engineer who owns all critical systems knowledge

• Dependencies with known critical vulnerabilities left unpatched

• No monitoring or alerting beyond basic uptime checks

• Architecture that can't scale without a full rewrite at the next order of magnitude

None of these are necessarily fatal. But each one becomes a negotiating point. Investors may reduce the valuation, add conditions to the term sheet, or require a technical remediation plan before funds are released.

How Engineering Teams Should Prepare

Start with a Self-Audit

Before any investor sees your codebase, you should see it yourself through their eyes. Run a structured internal review covering architecture, security, test coverage, infrastructure documentation, and dependency health.

Write down what you find. A written assessment that acknowledges known issues and outlines a remediation timeline is far more credible than a codebase that looks clean on the surface but hasn't been examined.

Get Your Infrastructure Documentation in Order

If your infrastructure lives in someone's head, that's a problem. Before due diligence starts, document how your systems are deployed, how they're monitored, and how you recover from failure. Infrastructure as code is the gold standard, but even clear written runbooks are better than nothing.

Address the Obvious Security Issues First

You don't need ISO 27001 certification to pass technical due diligence. You do need to show you take security seriously. Rotate any credentials that have ever been in version control. Implement secrets management. Make sure your CI/CD pipeline includes dependency vulnerability scanning. Document your access control policies.

Reduce Knowledge Concentration

If one engineer holds all the critical knowledge, start redistributing it now. Pair programming, internal documentation, and consistent code review all help. This takes time — which is exactly why it needs to start before the fundraise, not during it.

Prepare Your Team for the Interview Process

Technical due diligence often includes interviews with your engineering leads. Prepare them. They should be able to articulate the architecture clearly, explain the reasoning behind key technical decisions, and speak honestly about the areas that need work.

Investors aren't looking for perfection. They're looking for self-awareness and credibility.

When You Need External Help

Some founders run the preparation process internally. That works when you have a strong engineering lead who's been through due diligence before and has the bandwidth to run a structured audit alongside normal delivery.

Most scale-ups at post-seed to Series B stage don't have that. The CTO is either absent, stretched thin, or the same person who built the original system — and therefore has blind spots about it.

This is where an independent technical review adds real value. A fractional CTO or specialist firm can run the audit, identify the gaps, and help you fix them before the investor's reviewer finds them. That's a very different position to be in.

WireApps offers a Technical Readiness Report specifically for this situation: a fixed-scope pre-fundraise audit that gives you a clear picture of your technical posture before due diligence starts. It covers architecture, security, infrastructure, team structure, and delivery process. The output is a written report you can use internally to prioritise remediation — and share with investors as evidence of technical maturity.

The team has seen what investors look for across more than seven years of delivery. The Dome Capital case study is one example of that work in practice.

The Difference Between Passing and Sailing Through

There's a meaningful difference between a technical due diligence process that raises concerns and one that actively builds investor confidence.

The teams that sail through aren't the ones with perfect codebases. They're the ones who know their system well, have documented it honestly, and can speak credibly about both the strengths and the known limitations. They have a plan. They have evidence they execute against it.

That level of readiness doesn't happen in the two weeks between term sheet and close. It's the result of months of deliberate engineering practice: consistent code review, documented architecture decisions, infrastructure managed as code, and a team that shares knowledge rather than hoarding it.

If your fundraise is six months out, start now. If it's three months out, start this week. If the investor has already asked for access, call someone who has done this before.

Learn more at wireapps.co.uk.

FAQs

What is technical due diligence in a startup fundraise?
Technical due diligence is a structured review conducted by or on behalf of an investor to assess the quality, security, scalability, and team behind a startup's engineering. It typically covers codebase quality, infrastructure, security posture, architecture, and whether the engineering team can execute the roadmap. It's standard at Series A and above, and increasingly common at pre-seed and seed rounds.

How long does technical due diligence take?
Most processes run two to four weeks from access being granted to a final report. The timeline depends on the scope agreed with the investor, the complexity of the product, and how well-documented the engineering is. Preparation work done before the process starts can significantly reduce the time and the volume of follow-up questions.

What are the most common technical due diligence red flags?
The most common flags include low or absent test coverage, manual infrastructure with no documentation, security credentials stored in the codebase, a single engineer who holds all critical system knowledge, unpatched dependencies with known vulnerabilities, and no disaster recovery plan. Any of these can become conditions on a term sheet or a basis for valuation adjustment.

Can a startup fail a fundraise because of technical due diligence?
Rarely outright — but findings can delay a close, reduce a valuation, introduce conditions, or cause an investor to pass if the risk is significant enough. The more common outcome is that findings become negotiating points. Preparation reduces that risk considerably.

How should a founder prepare for technical due diligence?
Start with an internal or independent audit of your architecture, security, test coverage, infrastructure documentation, and team knowledge distribution. Document what you find and create a remediation plan for the gaps. Prepare your engineering leads to discuss technical decisions clearly and honestly. The goal is to demonstrate self-awareness and a credible plan — not a perfect codebase.

What is a Technical Readiness Report?
A Technical Readiness Report is a fixed-scope audit of a company's engineering posture, typically commissioned before a fundraise or an enterprise deal. It covers the same areas an investor's technical reviewer would examine and produces a written output that can be used to prioritise internal remediation and demonstrate technical maturity to investors. WireApps offers this as a standalone engagement.

How is technical due diligence different from a security audit?
A security audit focuses specifically on vulnerabilities, access controls, and compliance posture. Technical due diligence is broader — it covers security as one component alongside architecture, code quality, infrastructure, team structure, and delivery process. Some investors commission both. For most Series A and B fundraises, technical due diligence is the primary process, with security findings forming one section of the overall report.