example.js

const cachedVar = process.env.MY_ENV_VAR;
const cacheObject = structuredClone(process.env);
const cached = process.env.MY_ENV_VAR;
const loopsCount = 1_000_000;

function getEnvVarDirectly() {
  return process.env.MY_ENV_VAR;
}

function getEnvVarFromCache() {
  return cachedVar;
}

function getEnvVarFromCachedObject() {
  return cacheObject.MY_ENV_VAR;
}

console.time('Cached access from object');
for (let i = 0; i < loopsCount; i++) {
  getEnvVarFromCachedObject();
}
console.timeEnd('Cached access from object');

console.time('Cached access from variable');
for (let i = 0; i < loopsCount; i++) {
  getEnvVarFromCache();
}
console.timeEnd('Cached access from variable');

console.time('Direct access');
for (let i = 0; i < loopsCount; i++) {
  getEnvVarDirectly();
}
console.timeEnd('Direct access');