Is my SQL already strong enough for a data engineering interview?
Usually stronger than you expect, but tested differently. Analyst SQL optimises for getting the answer. Engineering SQL is judged on window functions, deduplication logic, incremental loads and performance on volume you cannot fit in memory. Expect to be asked why a query is slow and what you would change about the table rather than only whether you can produce the correct result set.
Do I need Spark, or is a warehouse and dbt enough?
It depends on the target. Product companies and startups on Snowflake, BigQuery or Databricks SQL will accept warehouse-plus-dbt fluency comfortably. Services organisations and large enterprises with Hadoop lineage still filter on Spark and PySpark by keyword. We choose based on the specific companies you are targeting, since learning both at once slows the transition down without improving either.
Will I lose the business context that makes me useful as an analyst?
Only if you let the transition erase it from your positioning. Domain knowledge is a genuine advantage in data engineering, because the expensive failures come from misunderstanding the data rather than the tooling. The right framing is that you build pipelines and can tell when the numbers coming out are wrong. Keep that on the resume alongside the engineering evidence, not instead of it.
How long should I expect this transition to take?
Longer than a tooling switch and shorter than a full career change, because half of the required knowledge already exists. The pacing usually depends on whether you can get pipeline work inside your current team. Analysts who can attach themselves to an existing data platform project build credible evidence in a couple of months. Those preparing entirely outside work should plan for a longer, steadier cycle.