_entry.twig

{% extends '_layouts/standard' %}

{% set cacheContentBlock = true %}

{% block content %}
    {# ...content worth caching #}
{% endblock %}

standard.twig

{% extends '_layouts/base' %}

{% block layout %}
    {% block navigation %}
        {% cache globally using key 'site-navigation' %}
            {% include '_includes/site/navigation' %}
        {% endcache %}
    {% endblock %}

    <main>
        {% set cacheContentBlock = cacheContentBlock ?? false %}
        {% set cacheKey = cacheContentBlock is same as(true) ? 'content-' ~ entry.id : cacheContentBlock %}

        {% cache globally using key cacheKey if cacheContentBlock %}
            {% block content %}
            {% endblock %}
        {% endcache %}
    </main>
{% endblock %}