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Pcs Research Group Software Engineer Interview Guide

Pcs Research Group Software Engineer interview guide: reported rounds, questions and how candidates describe the process.

The 60-second brief

The Software Engineer role at Pcs Research Group is a foundational position designed to bridge the gap between academic computer science concepts and enterprise-level software delivery. Engineers in this role contribute to building, optimizing, and maintaining data-driven applications that support the company's research, data modeling, and consulting pipelines. Because the company heavily emphasizes structured training and skill development, this role is highly focused on rapid technical growth, database mastery, and clean code construction. At its core, this position is critical to the organization’s capability to process and analyze complex data sets. As a Software Engineer, you will work closely with relational databases, write high-performance queries, and develop backend logic using languages like Java and Python.

This guide is scoped to a Software Engineer candidate at Pcs Research Group.

Focus areas

  • SQL
  • Technical Interview Round
  • Relational Databases

The Pcs Research Group interview process

Pcs Research Group candidates report 5 rounds over 4-6 weeks. The stages below are what candidates describe, not a published process.

Recruiter Call

Initial outreach or introductory phone call from a recruiter to explain the company's business model and employment terms.

What to demonstrate

  • Initial outreach or introductory phone call from a recruiter to explain the company's business model and employment terms
  • Depth in SQL

How to prepare

  • Be able to walk your CV end to end in two minutes, and say why this company specifically.
  • Have your salary expectations, notice period and location constraints ready, and ask for the rest of the loop in writing.

Online Assessment

Candidates complete an online test focusing on SQL, relational databases, logical reasoning, and basic math.

What to demonstrate

  • Candidates complete an online test focusing on SQL, relational databases, logical reasoning, and basic math
  • Depth in SQL

How to prepare

  • Answer aloud and timed: Write a SQL query using an INNER JOIN and a LEFT JOIN to combine data from two tables.
  • Answer aloud and timed: How do you optimize a slow-performing SQL query?

Study Preparation

After passing the online assessment, candidates receive specific study and prep materials for the technical rounds.

What to demonstrate

  • After passing the online assessment, candidates receive specific study and prep materials for the technical rounds
  • Depth in SQL

How to prepare

  • Answer aloud and timed: What is a primary key versus a foreign key, and how do they enforce referential integrity?
  • Answer aloud and timed: What are the four main pillars of Object-Oriented Programming, and how do you implement them?

Technical Interview

Mock interview or technical video round where candidates write queries and solve coding challenges live.

What to demonstrate

  • Mock interview or technical video round where candidates write queries and solve coding challenges live
  • Depth in SQL

How to prepare

  • Answer aloud and timed: What is the difference between a list and a tuple in Python?
  • Answer aloud and timed: Explain the concept of method overloading versus method overriding in Java.

HR Discussion

Final discussion with HR to finalize the terms of the offer and training agreement.

What to demonstrate

  • Final discussion with HR to finalize the terms of the offer and training agreement
  • Depth in SQL

How to prepare

  • Answer aloud and timed: Write a basic algorithm to reverse a string or find duplicate elements in an array.
  • Answer aloud and timed: How does memory management work in Java or Python?

Where candidates lose points

Prepare your local environment

Since the technical round may require screen sharing, make sure you have your local IDE (e.g., VS Code, Eclipse, PyCharm) open, configured, and ready to compile code in your language of choice.

Focus heavily on SQL basics

Do not overlook database fundamentals. Be ready to write joins, explain normalization, and write DML commands from memory without relying on auto-complete tools.

Review the provided prep materials

If the recruiter sends you study guides or preparation lists, dedicate significant time to reviewing them. The technical interview is highly aligned with these documents.

Be ready to discuss contract terms

Approach the conversation about training agreements with clarity. Ask detailed questions during the HR round to ensure you fully understand the commitments and expectations.

Questions & practice

Write a basic algorithm to reverse a string or find duplicate elements in an array.

Medium · Core Programming & OOP

Approach

  1. Restate the input: its shape, its size, and what is guaranteed about it.
  2. Name the brute-force solution and its complexity before improving on it.
  3. Choose the data structure from the access pattern, not from familiarity.
  4. State the target complexity and say which constraint rules the naive version out.

Follow-up

  • How does this change if the input no longer fits in memory?
  • What is the worst case, and how likely is it on real data?

How does memory management work in Java or Python?

Medium · Core Programming & OOP

Approach

  1. Say what the runtime actually does before reasoning about the code.
  2. Name what is shared across threads and what owns each piece of state.
  3. Identify the window where an invariant is briefly untrue.
  4. Distinguish a value from a reference to it, and say which one you handed out.

Follow-up

  • What happens if two callers reach this at the same time?
  • Where could this allocate more than you expect?

Track a rolling failure rate per destination for circuit decisions

Easy · sliding window · ring buffer · circuit breaker

The egress service delivers about 1,500 webhooks per second across roughly 40,000 destinations, each call bounded by a 10 second timeout. Maintain, per destination, the failure rate over the trailing 60 seconds so a caller can ask before dispatch whether the circuit should open. Attempts arrive as (destination_id, finished_at_ms, outcome). Requirement: amortised O(1) per attempt, with total memory bounded by the destination count rather than by traffic. Give the structure, its exact memory, and the rule that stops a destination with three attempts from opening a circuit.

Approach

  1. Name the exact-deque version and then reject it as the default. Holding timestamps and advancing a tail pointer past anything older than now minus 60 seconds is a correct two-pointer window at amortised O(1) per attempt, but its memory tracks in-window traffic, so one destination in a retry storm holds hundreds of thousands of entries while thousands of quiet destinations hold none.
  2. Use a ring of 60 one-second buckets per destination, each bucket a pair of counters for attempts and failures. On an attempt, advance the ring by the elapsed whole seconds, zeroing at most min(elapsed, 60) buckets, then increment the head. That is amortised O(1) with a fixed footprint per destination.
  3. State the footprint: 60 buckets times two 4-byte counters is 480 bytes of payload per destination, so 40,000 destinations is roughly 20 to 25 MB with per-entry overhead, bounded by the catalogue rather than by the rate. The cost is granularity, since the oldest bucket ages out in whole seconds, which is far tighter than the decision needs.
  4. Require a minimum sample before the circuit may open. A destination with three attempts and three failures reads as 100 percent and is not evidence; a floor of roughly 20 attempts in the window makes the ratio meaningful, and below that floor use a run of consecutive failures as the trigger instead.

Follow-up

  • The fleet is 30 instances and each sees roughly a thirtieth of a destination's traffic. Where does the rate actually live, and what does a per-instance answer get wrong?
  • A destination answers in 9.5 seconds and succeeds. It is not failing but it is consuming your per-destination concurrency. What signal should open the circuit here?

What is database normalization, and can you explain the differences between 1NF, 2NF, and 3NF?

Medium · SQL and Database Management

Approach

  1. Name the grain you start from and join outward from it.
  2. Check whether any join is one-to-many before aggregating, or the sums inflate.
  3. Say which index the query would use, and what makes it unusable.
  4. Handle the rows that do not match: that is usually the actual question.

Follow-up

  • How does the query change if that join becomes one-to-many?
  • What happens to this when the table is ten times larger?

Write a SQL query using an INNER JOIN and a LEFT JOIN to combine data from two tables.

Medium · SQL and Database Management

Approach

  1. Name the grain you start from and join outward from it.
  2. Check whether any join is one-to-many before aggregating, or the sums inflate.
  3. Say which index the query would use, and what makes it unusable.
  4. Handle the rows that do not match: that is usually the actual question.

Follow-up

  • How does the query change if that join becomes one-to-many?
  • What happens to this when the table is ten times larger?

How do you optimize a slow-performing SQL query?

Medium · SQL and Database Management

Approach

  1. Name the grain you start from and join outward from it.
  2. Check whether any join is one-to-many before aggregating, or the sums inflate.
  3. Say which index the query would use, and what makes it unusable.
  4. Handle the rows that do not match: that is usually the actual question.

Follow-up

  • How does the query change if that join becomes one-to-many?
  • What happens to this when the table is ten times larger?

How would you approach modeling a relational database schema for a simple e-commerce system?

Medium · Aptitude & Logical Reasoning

Approach

  1. Name the grain you start from and join outward from it.
  2. Check whether any join is one-to-many before aggregating, or the sums inflate.
  3. Say which index the query would use, and what makes it unusable.
  4. Handle the rows that do not match: that is usually the actual question.

Follow-up

  • How does the query change if that join becomes one-to-many?
  • What happens to this when the table is ten times larger?

Explain the difference between DML (Data Manipulation Language) and DDL (Data Definition Language) commands.

Medium · SQL and Database Management

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. Work from the requirement backwards to the design.

Follow-up

  • What assumption would you test first?
  • How would you know your answer was wrong?

What is a primary key versus a foreign key, and how do they enforce referential integrity?

Medium · SQL and Database Management

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. Work from the requirement backwards to the design.

Follow-up

  • What assumption would you test first?
  • How would you know your answer was wrong?

What are the four main pillars of Object-Oriented Programming, and how do you implement them?

Medium · Core Programming & OOP

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. Work from the requirement backwards to the design.

Follow-up

  • What assumption would you test first?
  • How would you know your answer was wrong?

What is the difference between a list and a tuple in Python?

Medium · Core Programming & OOP

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. Work from the requirement backwards to the design.

Follow-up

  • What assumption would you test first?
  • How would you know your answer was wrong?

Explain the concept of method overloading versus method overriding in Java.

Medium · Core Programming & OOP

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. Work from the requirement backwards to the design.

Follow-up

  • What assumption would you test first?
  • How would you know your answer was wrong?

Solve a logical deduction problem involving sequence patterns.

Medium · Aptitude & Logical Reasoning

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. Work from the requirement backwards to the design.

Follow-up

  • What assumption would you test first?
  • How would you know your answer was wrong?

Questions covering quantitative math, such as probability, percentages, and basic algebra.

Medium · Aptitude & Logical Reasoning

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. Work from the requirement backwards to the design.

Follow-up

  • What assumption would you test first?
  • How would you know your answer was wrong?

Read latency spikes on a sixty-second sawtooth

Medium · cache stampede · single-flight · ttl

The cached listing read path serves about 14k reads/second at an 85% hit rate. p99 sits at 35 ms for 57 seconds, jumps to 900 ms for 3, and repeats. During each spike the primary shows several hundred identical listing queries starting within the same millisecond, all carrying one large tenant's id. Cache entries use a 60-second TTL. Give the mechanism, the ordered checks, the fix, and the correctness hazard your fix must not introduce.

Approach

  1. Match the period to a configured number before theorising about load. A spike every 60 seconds against a 60-second TTL is an entry expiring, and you confirm it by correlating spike timestamps with the entry's write time rather than with the traffic curve. If the period had matched a cron or a GC interval instead, this is a different investigation.
  2. Establish the concurrency of the miss. Several hundred identical queries in one millisecond means the miss path has no coalescing: every request that arrives between expiry and repopulation recomputes. The herd size is that key's arrival rate times its recompute time, so at 1.2k reads/second for the hot key and a 250 ms recompute you expect about 300 concurrent misses, which matches what is observed.
  3. Add single-flight on the miss path so one caller per key recomputes under a short-lived lock while the rest wait for its result. Prefer stale-while-revalidate where the read tolerates it: return the expired value immediately and refresh asynchronously, which removes the latency spike rather than serialising it into a queue of waiters.
  4. De-synchronise the keys. Write TTLs with jitter, for example 60 seconds plus or minus 10%, so a deploy or a mass invalidation does not align every key on the same second and turn a per-key herd into a fleet-wide one.

Follow-up

  • The same sawtooth appears on a key that is invalidated on write rather than expired. Is that the same bug?
  • How does your answer change if the recompute takes 4 seconds instead of 250 ms?

Suggested practice checklist

Built from the rounds and topics Pcs Research Group candidates report.

Day 1 — Map the Pcs Research Group loop

  • Write out the reported sequence: Recruiter Call, Online Assessment, Study Preparation, Technical Interview, HR Discussion.
  • For each round, write one sentence on what it is judging, from the description above, and mark the one you are least ready for.

Deliverable: A one-page map of the 5 reported rounds, with the weakest marked.

Day 2 — Work SQL

  • Spend the session on SQL, which Pcs Research Group candidates report being tested on.
  • Write one worked example in SQL and time yourself on it.

Deliverable: One timed worked example in SQL.

Day 3 — Work Technical Interview Round

  • Spend the session on Technical Interview Round, which Pcs Research Group candidates report being tested on.
  • Write one worked example in Technical Interview Round and time yourself on it.

Deliverable: One timed worked example in Technical Interview Round.

Day 4 — Work Relational Databases

  • Spend the session on Relational Databases, which Pcs Research Group candidates report being tested on.
  • Write one worked example in Relational Databases and time yourself on it.

Deliverable: One timed worked example in Relational Databases.

Day 5 — Answer out loud: SQL and Database Management

  • Answer aloud, timed: Explain the difference between DML (Data Manipulation Language) and DDL (Data Definition Language) commands.
  • Answer aloud, timed: What is database normalization, and can you explain the differences between 1NF, 2NF, and 3NF?

Deliverable: Spoken answers to 2 reported SQL and Database Management question(s), under time.

Day 6 — Answer out loud: Core Programming & OOP

  • Answer aloud, timed: What are the four main pillars of Object-Oriented Programming, and how do you implement them?
  • Answer aloud, timed: What is the difference between a list and a tuple in Python?

Deliverable: Spoken answers to 2 reported Core Programming & OOP question(s), under time.

Day 7 — Answer out loud: Aptitude & Logical Reasoning

  • Answer aloud, timed: Solve a logical deduction problem involving sequence patterns.
  • Answer aloud, timed: Questions covering quantitative math, such as probability, percentages, and basic algebra.

Deliverable: Spoken answers to 2 reported Aptitude & Logical Reasoning question(s), under time.

Behavioural preparation

Behavioural rounds judge the decision you made and what it cost.

Why are you interested in joining the Software Engineer training program at Pcs Research Group?

Medium · Behavioral & Program Alignment

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. Name the disagreement and how you resolved it with evidence.

Follow-up

  • What would you do differently if you ran that again?
  • How did you know your change caused the improvement?

Describe a challenging technical project you worked on during your studies or previous employment.

Medium · Behavioral & Program Alignment

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. Name the disagreement and how you resolved it with evidence.

Follow-up

  • What would you do differently if you ran that again?
  • How did you know your change caused the improvement?

How do you handle receiving critical feedback on your code or technical performance?

Medium · Behavioral & Program Alignment

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. Name the disagreement and how you resolved it with evidence.

Follow-up

  • What would you do differently if you ran that again?
  • How did you know your change caused the improvement?

Are you comfortable working under a structured service agreement or contract?

Medium · Behavioral & Program Alignment

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. Name the disagreement and how you resolved it with evidence.

Follow-up

  • What would you do differently if you ran that again?
  • How did you know your change caused the improvement?