Fractional CTO for Series B Companies: Scope, Cost, Hiring

Why Series B Companies Still Hire Fractional CTOs

Series B is the upper bound of where fractional CTO scope still works. Companies at $10M to $30M ARR typically have a 15-30 person engineering team and a VP Engineering by this point. The fractional CTO provides strategic leadership across platform architecture, security and compliance maturation, M&A technical diligence, and the board-level technical narrative.

Past 30-40 engineers or $30M ARR, most companies need full-time CTO leadership. The fractional model breaks because the work is too constant, the team is too large, and platform decisions move too quickly for part-time presence. Companies that try to extend fractional past these thresholds typically discover the limits the hard way through outages, attrition, or product velocity decay.

Specific Scope at Series B

Series B fractional CTO scope is the most demanding tier of the fractional model. 25 to 35 hours per month covering:

• Platform architecture at multi-team scale
• VP Engineering management (already in place at this stage)
• Security and compliance maturation (SOC 2 Type II, possibly ISO 27001 or HIPAA)
• Hiring senior engineering leadership (Director level, principal engineers)
• Technical debt management with structured prioritization
• Vendor and cloud cost management at scale
• Cross-functional partnership at the executive level
• M&A technical due diligence (buy-side or sell-side)
• Pre-IPO technical readiness if applicable
• Board materials with sophisticated technical narrative

Carve-outs: full-time CTO scope (board ownership of all technology), day-to-day VP Engineering work, individual contributor performance management.

Pricing Benchmarks at Series B

Marketplace pricing through Toptal, A.Team, Bolster, or Catalant adds 25-40 percent on top.

Hiring Signals: When to Engage vs Hold Off

Engage when:

• Engineering team is 15-30 people and full-time CTO timing is unclear
• Compliance requirements are expanding (Type II audit, ISO, HIPAA)
• M&A activity is on the horizon and the team has no M&A diligence experience
• The board is signaling pre-IPO readiness or sale process within 18-24 months
• VP Engineering is strong but lacks executive-level technical strategy experience

Move to full-time CTO when:

• Engineering team past 30-40 people with continued growth
• The company is filing for an IPO within 12 months
• M&A activity is recurring (multiple deals per year)
• Technical strategy work has grown to 5+ hours per week of executive-level decisions
• The fractional CTO is consistently working 35+ hours per month

90-Day Milestones to Expect

Month 1: full engineering audit. Platform architecture review at multi-team scale. Security and compliance gap assessment. Technical debt prioritization framework rebuilt. VP Engineering capability evaluation.

Month 2: senior hire planning if applicable (Director, Principal). Compliance roadmap baseline (Type II, ISO, HIPAA). Cloud cost optimization assessment. Cross-functional partnership cadence at executive level established.

Month 3: technical narrative for next fundraise or sale process drafted. M&A readiness if applicable. Decision point on full-time CTO transition.

Picking the Right CTO at Series B

Series B fractional CTO selection is more demanding than earlier stages.

Have they led engineering at scale before? Going from 10 to 30 engineers is a different challenge than building from zero. Multi-team coordination, attribution at the team level, compliance maturation, vendor governance. These are scale-stage skills. Ask for specific companies they took through this transition.

Can they partner with a strong VP Engineering? By Series B the VP Engineering is already in place. The fractional CTO sits above them strategically, not in their lane. CTOs who try to manage individual engineers or run sprint planning at Series B end up duplicating VP Engineering work. The right CTO at this stage is a thought partner and external advocate, not an operator.

Do they have M&A or pre-IPO experience? Series B is when M&A activity starts and pre-IPO conversations begin. A fractional CTO without these experiences puts a ceiling on the role's value. Ask which transactions they've supported and what their actual scope was.

The Pre-IPO Track

If the company is on a pre-IPO track, the fractional CTO arrangement usually has 12-18 months of useful life. The work that comes with public-readiness (SOX-equivalent technical controls, security incident reporting, IR-coordinated technical narrative) is full-time CTO scope. The fractional CTO often supports the search, runs the technical strategy through transition, and stays as an advisor through the close.

For broader context, see fractional CTO responsibilities and fractional CTO retainer.

Where Fractional Series B CTO Engagements Fail

The leading failure mode at Series B is duplication with VP Engineering. The CTO and VP Engineering have overlapping authority and the team gets mixed signals. The fix: explicitly define who owns what (CTO: platform strategy, hiring leadership, M&A, board narrative; VP Engineering: team management, sprint operations, IC performance). Re-baseline the boundary quarterly.

The second failure is hours scale. The retainer was sized for 30 hours per month at signing. By month 6, the actual work is 50 hours per month. Re-baseline at month 4-5 when the actual scope becomes clear.

The third failure is misaligned authority on hiring senior engineers. By Series B, hiring decisions involve the CTO, the VP Engineering, and often the CEO. Without explicit authority allocation, hiring slows because three people need to align on every senior offer. Spell out who has final say on Director-level and Principal-level hires.