Coding is the Easy Part
By the time you reach 5 years of experience, writing complex algorithms is expected. It is the baseline. What pushes you from a 'Mid-Level' to a 'Senior' or 'Staff' engineer is your ability to navigate the business side of the company.
Pushing Back Professionally
A junior developer says 'Yes' to every feature request, works until 2 AM, and burns out. A senior developer says: 'We can build that, but it will delay the core launch by 3 weeks. Is this feature critical for the MVP?'
Translating Tech to English
The CEO doesn't care that the database is deadlocking due to unindexed queries. A senior engineer translates this: 'Our system cannot handle the current sales volume. I need 3 days to optimize the infrastructure, or the site will crash on Friday.'