Study core CS fundamentals
The interview-grade bar in OS, DBMS, SQL, networks, OOP and concurrency, the hours it gets, and the drill that makes it stick.
This track covers the operating systems, databases, networking, and programming concepts that support backend interviews. The week template reserves part of its four-hour fundamentals and LLD block for these topics.
The bar is fresher-level and interview-grade, not academic. In practice it is deadlock, CPU scheduling, paging, normalisation, ACID, indexing, HTTP, TCP, TLS and the OOP pillars.
What to focus on
Fundamentals are the cheapest questions an interviewer can ask, so they come early. A hesitant answer on deadlock sets the tone for the rest of the round.
The cost is asymmetric. A missed hard DSA problem is one problem. A wrong answer on paging or ACID reads as "has not built anything", which is the exact signal your projects are meant to send.
10 hours a week overshoots. The round asks you to explain crisply, not defend an OS thesis.
The three levels
Every topic and resource carries one tag. Read it before you spend a week.
| Level | What it means |
|---|---|
| SDE-1 must | Needed for the SDE-1 interviews this plan targets. Do it now. |
| SDE-1 nice | Useful before the offer, once the must list is clean. |
| SDE-2 later | Read after you have an offer, or on the job. Skip it now. |
The six subjects
| Subject | Why it matters | When | SDE-1 priority |
|---|---|---|---|
| Operating systems | Process vs thread, deadlock, scheduling and paging come up in every loop. | Weeks 1 to 2 | SDE-1 must |
| DBMS | Transactions, isolation and indexes are the theory behind Ledgerline. | Weeks 2 to 3 | SDE-1 must |
| SQL | You will write a join and read a query plan. | Weeks 2 to 4 | SDE-1 must |
| Networks | TCP, TLS and HTTP appear in every backend round. | Weeks 3 to 4 | SDE-1 must |
| Concurrency | Job descriptions test it, and Logsmith consumer groups use it. | Weeks 6 to 7 | SDE-1 must |
| OOP | The four pillars and SOLID are the vocabulary LLD assumes. | Weeks 4 to 5 | SDE-1 must |
Suggested order
Start with operating systems. It gives you the words the other five use: process, thread, lock, page.
Read DBMS next. ACID and isolation are the theory behind the ledger you build in weeks 2 to 7.
Follow with SQL. It is the practice half of DBMS, and EXPLAIN ANALYZE needs the index story you just read.
Take networks fourth. It borrows the process and socket model from OS and needs no database reading.
Do concurrency fifth. It is easier once OS synchronisation is fresh, and it lands with the Logsmith build.
Leave OOP for last. It is the smallest subject and your coursework covers it best, so it costs least at the end. It also hands into LLD.
The hours rule
Use the planned fundamentals block alongside LLD practice. If a week becomes too full, review the most relevant questions and keep the rest for a later pass.
The method: out loud, recorded
Every answer is spoken and recorded, 60 to 90 seconds each. Record on your phone, listen once, note where you stalled, then move on. Do not script the answers.
Silent reading creates confidence the interview does not reward. If you can say it in 90 seconds, you know it.
Tie every answer to a project. "In Ledgerline I avoided deadlock by ordering account IDs before locking" is a different sentence from a definition.
One subject a week
The 6-week drill plan holds every question, one subject per week, plus the two concurrency talks to read before the concurrency week.
Question banks
| Source | What it gives you | URL |
|---|---|---|
| KnowledgeGate bank | The drill source: a fresh-interview OS, DBMS, CN and OOP set | knowledgegate.ai |
| GfG question set | A cross-check on depth | geeksforgeeks.org |
| InterviewBit | 70+ networking questions | interviewbit.com |
Start here
Open operating systems for week 1. Read the SDE-1 scope table, answer the ten questions out loud, and only then read the SDE-2 section if the week has room.
The 6-week drill plan is the work. This page is the map.