The private markets have become subject to a frenzy of investment interest from investors over the much of the last 15 years thanks in large part to the historic period of near rock-bottom interest rates.

Now, Darian Shirazi of Alphabet-backed Gradient Ventures is raising concerns about how much longer it can last.

With the U.S. officially in the beginning stages of what is expected to be a far higher interest rate environment, a dramatic recalculation away from riskier asset classes is setting off alarm bells for Shirazi, who leads the early-stage-focused venture capital firm and tells Fortune that, with big-scale investors set to start pulling back from venture capital funds, the heads of private companies need to be prepared for the fallout to come with it—whether that be down rounds, layoffs, or consolidation.

"It is important to realize that the tables have and will continue to turn," Shirazi wrote in an emailed memo to company founders on March 28 that harkens back to Sequoia Capital's now-infamous "R.I.P. Good Times" letter from 2008. "Financings will take longer and terms will be less favorable to companies. The sooner you become aware of this dynamic and that it is macro-related and not specific to you, the more likely you will be to survive."

From Wall Street to Silicon Valley, the Federal Reserve's path toward higher interest rates—accelerated largely by the escalating threat of inflation—has been well forecasted for months now, leading investors to begin planning accordingly by moving out what they see as riskier assets like cryptocurrencies and technology stocks and into safer ones like bonds.

The results, between technology stocks selling off, IPOs coming to a standstill, and fundraising activity drying up in the private markets, have left startup founders puzzled, though, Shirazi tells Fortune.

Companies have for years followed a seemingly tried-and-true track of raising money from venture capitalists, scaling up, hopefully turning a profit, and then going public. Now, founders are finding some speed bumps along the way, leading them to ask, "What's wrong with my company?" But the reality is that the macroeconomic conditions are shifting from a tailwind to a headwind—something that founders don't tend to think about on a daily basis, Shirazi says.

It's a situation that will ultimately force many companies to accept lower valuations than in prior fundraises, Shirazi predicts, as it is one that will prompt more companies to seek out potential buyers. But there is hope, the venture capitalist wrote in the emailed memo, should companies prioritize balancing growth and capital efficiency.

"We went from a period where money was basically everywhere [to one] where suddenly money is very difficult to come by for companies at the series B or later stage," Shirazi tells Fortune. "The sooner you can become more efficient, the more likely you are to succeed."

Shirazi had four pieces of advice for company founders to maximize their chances of survival "in this new era":

·Stockpile between 18 to 24 months of runway, "regardless of your scale."

·Lay people off "sooner than you think you need to" and "strongly incentivize" those that remain.

·Cut the burn rate.

·Talk to the board about "everything that could harm or kill your business" and come up with plans of action for each. "Some boards may not want to hear bad news," Shirazi writes, "but it is important you discuss all risks with your fellow founders, executives, and board members now so you can make changes as needed."