Is it possible to customize a block which load data from database

Sure, but in that case, I'd suggest you create a custom component.

Here an example/pseudo-code of triggering an async function for changing the component content

editor.DomComponents.addType('my-custom-component', {
	model: {
		defaults: {
			endpoint: 'http://A', // some prop for the trait
			traits: [
				{
					type: 'select',
					name: 'endpoint',
					changeProp: 1,
					options: [ 'http://A', 'http://B' ],
				}
			]
		},
		init() {
			this.listenTo(this, 'change:endpoint', this.refreshContent);
			this.refreshContent();
		},
		async refreshContent() {
			const { endpoint } = this.attributes;
			const response = await fetch(endpoint);
			...
			let result = '';
			// ... Build the HTML result from the async response
			...			
			this.components(result);
		}
	}
});