Lightning Web Components Overview

Lightning Web Components (LWC) is a programming model used to build custom HTML elements. These custom elements, the web components, are made using HTML and modern JavaScript. Because of this, LWC is an efficient way to add high-performing custom elements. LWC is an open-source technology.

Lightning Data Service Overview

Lightning Data Service (LDS) caches and shares records across components. LDS provides performance improvements by loading a record only once for use by multiple records on a page. LDS manages data for you, and changes to a record are reflected in all components using that record. LDS is built on top of the User Interface API (UI API), making it easy to create Salesforce pages. These pages are efficient because data requests return both data and metadata.

LDS helps code perform well by loading the record data and caching it client-side. Using the cached data is faster than requesting this data from the server. The cache is updated with server requests at the end of its lifetime. This results in fewer server requests. It is important to note that the cache timeout is separate from the layout timeout, so changes to the layout will only be displayed if you reload after the timeout or log out and log back in.

LDS is not an open-source technology. It requires the Salesforce server to run.

How does this impact Pulsar?

Unless Salesforce decides to open-source the Lightning Data Service, only Salesforce can run both the Lightning Web Components and the Lightning Data Service at this time. This means that you must be online to update pages using these technologies, and they will only work offline with the cached data. While designing your pages and planning to use Pulsar, if you use both LWS and LDS, keep in mind that your pages will only display the cached data as of when the user went offline. Those pages will update when the user goes back online.