Platform Developer I tests whether you can write code that works on Salesforce specifically, not just code in general. Most people who struggle know how to program; what trips them up is the platform: shared resources, limits, the order things run in, and when not to write code at all.
Know when not to write code
Many questions describe a requirement and ask for the best solution. If a formula field, validation rule or flow does the job, that is usually the answer. Knowing what the platform does without code is part of being a Salesforce developer, which is why Arkton’s path puts Administrator first.
The topics that matter most
Developer fundamentals
The data model, multi-tenancy and why governor limits exist. Salesforce runs many customers on shared infrastructure, so every transaction has limits on queries, DML statements and CPU time.
Apex core
Classes and methods, collections, SOQL and SOSL, and DML. Be comfortable querying related records and working with lists, sets and maps.
Advanced Apex
Triggers and the order of execution, bulk-safe code, exception handling, and asynchronous Apex: future methods, queueable, batch and scheduled Apex. Expect scenarios where the right answer is the one that still works for two hundred records at once.
User interface
Lightning Web Components: how they get data, how they talk to Apex, and how components communicate.
Testing and deployment
Test classes, creating test data, and deployment. Code needs at least 75% test coverage to deploy to production, and good tests assert results rather than just running lines.
Write bulk-safe code from the start
The single most useful habit: never put a query or DML statement inside a loop. Collect what you need, query once, change records in a list, and save once. It is the pattern behind a large share of exam questions and of real-world bugs.
Practise on a real org
Use a free Developer Edition org or a scratch org. Write a trigger, break it on purpose with a bulk data load, then fix it. Writing and running tests yourself is the fastest way to understand coverage and test isolation.
Check the official guide
The exam guide on Trailhead lists the current sections and weighting. Use it as your checklist.
How Arkton helps
The Platform Developer I course covers developer fundamentals, Apex, advanced Apex, user interface, and testing and deployment in 25 lessons, with hands-on labs and exam preparation: about 23 hours of material, scheduled around your exam date.