local function insert (key, value, lock_id, lifetime_milliseconds, idle_timeout_milliseconds, additional_keys)
    if is_locked_by_another_owner(key, lock_id) or is_any_locked_by_another_owner(additional_keys, lock_id) then
        return { "locked_by_other" }
    end

    if get_existing_entry(key) then
        debugLog("failed to insert new entry because entry for key '%s' already exists", key)
        return { "already_exists" }
    end

    set_value(key, value, nil, lifetime_milliseconds, idle_timeout_milliseconds, additional_keys)
    debugLog("successfully inserted key '%s' with new value", key)
    return { "ok", value }
end

local function update (key, value, lock_id, lifetime_milliseconds, idle_timeout_milliseconds, new_additional_keys)
    if is_locked_by_another_owner(key, lock_id) or is_any_locked_by_another_owner(new_additional_keys, lock_id) then
        return { "locked_by_other" }
    end

    local existing_entry = get_existing_entry(key)
    if not existing_entry then
        return { "not_found" }
    end

    local existing_additional_keys = existing_entry.additional_lock_keys
    if is_any_locked_by_another_owner(existing_additional_keys, lock_id) then
        return { "locked_by_other" }
    end

    local combined_additional_keys = combine(existing_additional_keys, new_additional_keys)
    set_value(key, value, existing_entry.creation_time_milliseconds, lifetime_milliseconds, idle_timeout_milliseconds, combined_additional_keys)

    debugLog("successfully updated key '%s' with new value", key)
    return { "ok", value }
end