Will Fastly's top 10 customer revenue concentration exceed 36% in any quarter reported by Q3 2026?

The 3-quarter trend is 31% to 32% to 34%, with the Q4 jump of 2pp suggesting possible acceleration. The growth differential (top 10 at 28% YoY vs rest at 20%) mathematically drives concentration higher unless the rates converge -- and there is no evidence of convergence. The company stopped reporting total customer count, which Moat Mapper flagged as concerning for new customer acquisition visibility. With three quarters of opportunity (Q1, Q2, Q3 2026), even at the slower +1pp/quarter pace, concentration would reach ~37% by Q3. The Q4 acceleration could push the breach earlier. The streaming entertainment cluster at ~12% of revenue creates additional concentration fragility that could amplify the trend if those entities expand further.

The mathematical relationship between top-10 growth (28%) and rest-of-base growth (20%) is the core driver. For concentration to stop rising, those growth rates must converge, and the context provides no evidence of convergence. The discontinued total customer count reporting (noted by Moat Mapper) raises concerns about new customer acquisition offsetting concentration. However, base effects matter -- as top 10 becomes a larger revenue share, maintaining 28% growth on a larger base becomes harder. The resolution requires strictly more than 36%, and companies sometimes round these figures. Three chances to cross reduces the probability of a miss. The unresolved debate about whether the Q4 2pp jump is structural or episodic is the key uncertainty -- structural acceleration makes this highly likely, episodic means it may stabilize near 35-36%.

The trend is clearly upward at 31% to 32% to 34% over three quarters, but the pace is ambiguous -- the +1pp then +2pp pattern could reflect either acceleration or a one-time large customer ramp in Q4. If the Q4 jump is episodic, concentration could stabilize in the 34-36% range without cleanly crossing >36%. The resolution requires explicit disclosure of top 10 concentration exceeding 36%, and there is a small probability the company discontinues this disclosure (which resolves NO). However, the structural growth differential (40% faster for top 10) and three reporting opportunities favor eventual breach. The survivorship bias concern from Moat Mapper -- that strong retention metrics reflect a self-selected customer base -- suggests the non-top-10 base may be weaker than headline metrics imply, supporting continued concentration.

The math is straightforward: 31% to 32% to 34% over three quarters, with top 10 growing 40% faster than the rest of the base. At even the conservative +1pp/quarter pace, concentration reaches 35% Q1, 36% Q2, 37% Q3 -- breaching >36% in Q3. At the accelerating pace implied by the Q4 2pp jump, breach could come as early as Q1 or Q2. Multi-product adoption at 50% of customers generating 75% of revenue shows power-law dynamics that structurally favor the largest accounts. Three chances to cross makes this more likely than not. The only scenario for NO is if a major top-10 customer churns or dramatically reduces spend, and there is no evidence of that in the analysis.

The directional trend is clear but the pace matters for the specific >36% threshold. The Q4 2pp jump could be a one-time large enterprise ramp that does not repeat. If concentration reverts to +1pp/quarter: 35% Q1, 36% Q2, 37% Q3. Breach only occurs cleanly in Q3, and the pace could slow further if Fastly successfully diversifies its customer base through new enterprise wins. The streaming entertainment cluster at ~12% introduces two-way risk -- expansion pushes concentration higher, but reduction or renegotiation could suppress it. The meta-synthesis ranked customer concentration stabilizing below 36% as a key conditionality for the thesis, suggesting the company may be actively managing against this threshold. Still more likely than not given three opportunities.

The growth differential is structural, not episodic. Top 10 customers are large enterprise accounts consuming CDN, security, and compute products -- the multi-product adoption data (50% of customers using 2+ products, generating 75% of revenue) confirms power-law dynamics favoring the largest accounts. Enterprise customer count grew from 596 to 628, but this modest growth in the denominator is insufficient to offset the top-10 growth differential. With NRR at 110%, existing large customers are expanding faster than new customers can dilute their share. Three quarterly reporting windows provide ample opportunity for the 34% starting point to cross >36%. The concentration trend would need to reverse, not merely slow, to avoid breach by Q3.

Concentration trend is 31% to 32% to 34% over 3 quarters. Top 10 growing 28% vs rest at 20%. At +1pp/quarter, reaches 37% by Q3 2026. Three chances to cross >36%. Growth differential is the mathematical driver and shows no sign of converging. More likely than not to breach.

Starting at 34%, need >36% in any of Q1-Q3 2026. At the average pace of +1.5pp/quarter (averaging +1pp and +2pp jumps), would reach 35.5% Q1, 37% Q2. Even at slower +1pp pace: 35% Q1, 36% Q2, 37% Q3. The growth differential (28% vs 20%) sustains upward pressure. Some risk that pace slows if top-10 base effects kick in, but three chances is a wide window.

Concentration rising steadily from 31% to 34% over three quarters. Growth differential is persistent and structural. Multi-product adoption at 50% generating 75% of revenue confirms power-law dynamics favoring top accounts. Three quarterly reports to cross >36%. Most likely breach occurs by Q2 or Q3 2026.