“The people are tired of getting by,” said Raul Anzola, the manager of the 1956 Lounge & Bar, which hosted the party. “They want to spend, they want to live.”

Almost overnight, the country’s authoritarian leader, Nicolás Maduro, has made that possible — for some.

With the country’s economy derailed by years of mismanagement and corruption, then pushed to the brink of collapse by American sanctions, Mr. Maduro was forced to relax the economic restraints that once defined his socialist government and provided the foundation for his political legitimacy.

The changes have helped transform Venezuela in ways few in Washington or Caracas had envisioned, but that are reminiscent of how its allies, Cuba and Nicaragua, relaxed Communist policies and allowed some private investment when faced with economic collapse in previous decades.

After years of nationalizing businesses, determining the exchange rate and setting the price of basic goods — measures that have long contributed to chronic shortages — Mr. Maduro seems to have made peace with the private sector and let it loose. And while the country’s economy continues to contract overall, the declining regulations have encouraged companies serving the wealthy or the export market to invest again.