Salesforce Fundamentals
The platform in one paragraph
Salesforce is a multitenant, metadata-driven platform: customers share application servers and database infrastructure, and your customizations live as metadata rather than in a forked copy of the product. Two consequences drive most exam questions. First, because resources are shared, every request runs inside governor limits - a per-transaction budget for SOQL queries, DML statements, records touched, CPU time and heap. Second, because behavior is defined by metadata, deployment is a metadata operation rather than a server install.
Concepts you must be able to name
- MVC split: objects and fields (model), page layouts, Lightning pages and Visualforce (view), and Apex triggers, flows and validation rules (logic).
- Declarative before programmatic: flows, validation rules, formula fields and roll-up summaries first; Apex when you need callouts, cross-record transactions, or complexity the declarative tools cannot express.
- Synchronous vs asynchronous: synchronous requests get roughly 100 SOQL queries, 150 DML statements, 10 seconds of CPU and 6 MB of heap; asynchronous Apex (future, queueable, batch) gets a larger budget, around 200 queries, 60 seconds and 12 MB. Limits reset per transaction, though a few (API calls) are measured over 24 hours.
- Security still applies: multitenancy does not mean shared visibility. Profiles, permission sets, field-level security and sharing rules govern access, which is why
with sharingmatters on Apex classes.
Trap
A question shows a trigger looping over Trigger.new and querying inside the loop. The problem is not speed; it is that the 101st record blows the SOQL limit. Collect the Ids, query once, and index results in a Map<Id, SObject>.
Rule of thumb
One transaction equals one limit budget. Before asking "how long does this take?", ask "how many times does this line execute per transaction?"