cy.exec() taking a lot longer than the underlying command (but successful)

[foucdeg]

I use a cy.exec call to find the ID of my server's Docker container by its service name, and then run a command on it.

Cypress.Commands.add('runBackendCommand', (command) => {
  cy.log(`Running command \`${command}\` against the backend`);
  cy.exec('docker ps -aqf "name=backend"').then(
    ({ stdout }) => {
      const backendContainer = stdout.trim();
      cy.log("backendContainer", backendContainer)
      return cy.exec(`docker exec ${backendContainer} ${command}`);
    },
  );
});

The first call, cy.exec('docker ps -aqf "name=backend"'), takes around 30 seconds within Cypress. But it is eventually successful, backendContainer gets logged.
Calling it directly in a terminal returns in under a second with one line of stdout and a zero status.
What could explain such a difference in duration?