insert(key, data, expiry_ts) {
        // Throw on overwrites
        if (this.#container[key])
            throw new Error('MemoryStore: key ' + key + ' already exists. Use update() method.');

        this.#container[key] = {
            data: data,
            expiry: expiry_ts,
        };
    }
@param {String} key
@param {Object} data
@param {Number} expiry_ts In Milliseconds