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Proxiad Software Engineer Interview Guide

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

The 60-second brief

As a Software Engineer at Proxiad, you play a vital role in delivering high-quality, customized IT consulting and software development services to a diverse portfolio of enterprise clients. Proxiad operates as a strategic technology partner, meaning its engineering teams do not just write code in isolation; they design, optimize, and integrate robust software ecosystems that solve complex business challenges for global brands. From digital transformation initiatives in financial services to scalable e-commerce platforms and cloud migrations, your technical contributions directly impact client operations and user experiences. What makes this role uniquely engaging is the consulting dynamic.

This guide is scoped to a Software Engineer candidate at Proxiad.

Focus areas

  • Java
  • Spring Framework
  • Object-Oriented Programming (OOP)

The Proxiad interview process

Proxiad candidates report 4 rounds over 3-5 weeks. The stages below are what candidates describe, not a published process.

Initial Technical Assessment

Begin with a technical assessment on platforms like CodingGame to filter for core programming competency.

What to demonstrate

  • Begin with a technical assessment on platforms like CodingGame to filter for core programming competency
  • Depth in Java

How to prepare

  • Answer aloud and timed: Explain the difference between object-oriented programming and functional programming in Java.
  • Answer aloud and timed: How does multithreading work in Java, and how do you prevent race conditions?

Introductory Interview

Meet with HR or a recruiter to discuss career goals, motivations, and fit for consulting roles.

What to demonstrate

  • Meet with HR or a recruiter to discuss career goals, motivations, and fit for consulting roles
  • Depth in Java

How to prepare

  • Answer aloud and timed: What are the differences between various implementations of the Java Collections Framework (e.g., ArrayList vs. LinkedList, HashMap vs. TreeMap)?
  • Answer aloud and timed: Can you explain how generics work under the hood, specifically concepts like type erasure?

Core Technical Evaluation

Engage in a deep-dive interview with a Technical Referent or Tech Lead, covering theoretical questions and coding tests.

What to demonstrate

  • Engage in a deep-dive interview with a Technical Referent or Tech Lead
  • Covering theoretical questions and coding tests

How to prepare

  • Answer aloud and timed: Describe your low-level understanding of the JVM, garbage collection, and memory allocation.
  • Answer aloud and timed: Explain the core concepts of the Spring Framework, including Dependency Injection and Aspect-Oriented Programming (AOP).

Commercial Evaluation

Meet with commercial managers or sales directors to discuss client accounts and ensure alignment with active client needs.

What to demonstrate

  • Meet with commercial managers or sales directors to discuss client accounts and ensure alignment with active client needs
  • Depth in Java

How to prepare

  • Answer aloud and timed: What is the difference between Spring Boot and the standard Spring Framework?
  • Answer aloud and timed: How does Hibernate handle dirty checking, and how do you optimize database transactions?

Where candidates lose points

Structure your background pitch

Be prepared to talk through your career history chronologically, highlighting not just what you built, but the business value your solutions delivered to past employers or clients.

Brush up on computer science fundamentals

Do not neglect basic sorting, searching, and algorithm complexities. Even experienced developers are sometimes tested on these core concepts during the technical rounds.

Some candidates have reported instances of "silence radio" or delayed communication after technical interviews

Do not hesitate to politely follow up with your recruiter if you have not heard back within a week of your technical evaluation.

Questions & practice

How does multithreading work in Java, and how do you prevent race conditions?

Medium · Java & Core Development

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?

Describe your low-level understanding of the JVM, garbage collection, and memory allocation.

Medium · Java & Core Development

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?

Walk through the time and space complexity of common sorting and searching algorithms.

Medium · Algorithms & Architecture

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?

Write a complex SQL query involving multiple joins, aggregations, and subqueries.

Medium · Enterprise Frameworks & Databases

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?

Stop tag and share joins from fanning out a page

Medium · join fan-out · semi-joins · many-to-many

resource_tag is (resource_id, tag_id) with PK (resource_id, tag_id); resource_share is (resource_id, shared_with_user_id, permission). The tagged-and-shared listing inner-joins resource to both, filters tenant_id, tag_id = ANY($2) and shared_with_user_id = $3, orders by updated_at DESC and takes 50. Pages come back with fewer than 50 distinct resources and the total in the header is far too high. Explain the row multiplication, rewrite both the page query and the count query so each is correct, and name the index each one needs. PostgreSQL 16.

Approach

  1. Do the arithmetic against the predicates that are actually there. An inner join emits one row per matching child row, and both joins are filtered: tag_id = ANY($2) admits only the requested tags, shared_with_user_id = $3 admits one user's share rows. So a resource holding three of the requested tags and shared with $3 once yields three rows, not one — the multiplier is its count of matching tags times its share rows for that single user, and that second factor is 1 unless the table admits duplicate (resource_id, shared_with_user_id) pairs. LIMIT 50 then limits rows rather than resources, and COUNT(*) counts pairs — the header is the product, not the population.
  2. Reject DISTINCT as the fix. It deduplicates after the product has been built, so the planner must materialise and sort the fanned-out set before the LIMIT can apply, and it leaves any SUM or AVG in the same select list wrong.
  3. Rewrite both filters as semi-joins, keeping resource as the only row source: AND EXISTS (SELECT 1 FROM resource_tag rt WHERE rt.resource_id = r.resource_id AND rt.tag_id = ANY($2)) and the same shape against resource_share. A semi-join stops at the first match per resource and preserves the driving index order, so ORDER BY updated_at DESC, resource_id DESC LIMIT 50 still stops after 50 rows.
  4. Count with the same predicates and no join at all: SELECT count(*) FROM resource r WHERE r.tenant_id = $1 AND r.status = 'active' AND EXISTS (...) AND EXISTS (...). Nothing multiplies a resource, so the number is the population.

Follow-up

  • The filter changes from 'any of these tags' to 'all of these tags'. Rewrite it and state what it costs relative to the ANY form.
  • A resource can be shared with the same user twice under different permissions. Does your count change, and should it?

Explain the difference between object-oriented programming and functional programming in Java.

Medium · Java & Core Development

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 differences between various implementations of the Java Collections Framework (e.g., ArrayList vs

Medium · Java & Core Development

What are the differences between various implementations of the Java Collections Framework (e.g., ArrayList vs. LinkedList, HashMap vs. TreeMap)?

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?

Can you explain how generics work under the hood, specifically concepts like type erasure?

Medium · Java & Core Development

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 core concepts of the Spring Framework, including Dependency Injection and Aspect-Oriented Programm

Medium · Enterprise Frameworks & Databases

Explain the core concepts of the Spring Framework, including Dependency Injection and Aspect-Oriented Programming (AOP).

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 Spring Boot and the standard Spring Framework?

Medium · Enterprise Frameworks & Databases

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?

How does Hibernate handle dirty checking, and how do you optimize database transactions?

Medium · Enterprise Frameworks & Databases

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?

How would you design a scalable microservices architecture for a high-traffic client platform?

Medium · Algorithms & Architecture

Approach

  1. Fix the scope first: who calls this, how often, and what they do when it fails.
  2. Name the read and write paths separately; they rarely have the same bottleneck.
  3. Choose a partition key and say what query it makes expensive.
  4. State the consistency you need, and where you are willing to be stale.

Follow-up

  • What breaks first when traffic grows ten times?
  • How does this behave when that dependency is down for an hour?

Explain some of the common design patterns (e.g., Singleton, Factory, Strategy) and when you would use them.

Medium · Algorithms & Architecture

Approach

  1. Fix the scope first: who calls this, how often, and what they do when it fails.
  2. Name the read and write paths separately; they rarely have the same bottleneck.
  3. Choose a partition key and say what query it makes expensive.
  4. State the consistency you need, and where you are willing to be stale.

Follow-up

  • What breaks first when traffic grows ten times?
  • How does this behave when that dependency is down for an hour?

How do you structure an application to ensure high availability, fault tolerance, and clean separation of conc

Medium · Algorithms & Architecture

How do you structure an application to ensure high availability, fault tolerance, and clean separation of concerns?

Approach

  1. Fix the scope first: who calls this, how often, and what they do when it fails.
  2. Name the read and write paths separately; they rarely have the same bottleneck.
  3. Choose a partition key and say what query it makes expensive.
  4. State the consistency you need, and where you are willing to be stale.

Follow-up

  • What breaks first when traffic grows ten times?
  • How does this behave when that dependency is down for an hour?

One log partition stops advancing while the others drain

Easy · poison message · head-of-line blocking · consumer lag

Search results for a subset of tenants are hours stale; the rest are current. The projection consumer reports lag of zero on 15 of 16 partitions and 400,000 on one. Its error rate is flat and its CPU is idle. outbox_event has no pending rows older than a second, so the relay has published everything it holds. Identify the mechanism, give the ordered checks, and state what you do in the first ten minutes versus what you change permanently.

Approach

  1. Read the lag distribution first. A slow consumer lags everywhere; zero on fifteen partitions and 400,000 on one is not throughput. Idle CPU on the stuck partition means the consumer is not advancing its offset at all, which points at one message it cannot get past rather than at a rate problem.
  2. Exonerate the producer before touching the consumer. No pending outbox rows older than a second means the relay published, so the event exists in the log. This separates never sent from sent and never applied, which are different code paths and usually different owners.
  3. Read the message at the stuck offset and the handler's log lines for its event_id. A flat error rate with no progress has two explanations and you must distinguish them: the handler is throwing and the retry loop is swallowing it, or the handler is blocking on something and never returning. Idle CPU with no error lines favours the second.
  4. Mitigate before diagnosing further. Move the offending event to a dead-letter store and commit the offset past it. Adding consumers does nothing here, because a partition is consumed by exactly one member of the group, and the blast radius is every aggregate hashed to that partition, not only the aggregate that produced the bad event.

Follow-up

  • The dead-lettered event carried aggregate_version 7 and the projection had applied 6. What must the replay do differently if 8 and 9 landed in the meantime?
  • How do you show staleness to the user while the partition is behind, given the API already returns the projection's watermark?

Suggested practice checklist

Built from the rounds and topics Proxiad candidates report.

Day 1 — Map the Proxiad loop

  • Write out the reported sequence: Initial Technical Assessment, Introductory Interview, Core Technical Evaluation, Commercial Evaluation.
  • 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 4 reported rounds, with the weakest marked.

Day 2 — Work Java

  • Spend the session on Java, which Proxiad candidates report being tested on.
  • Write one worked example in Java and time yourself on it.

Deliverable: One timed worked example in Java.

Day 3 — Work Spring Framework

  • Spend the session on Spring Framework, which Proxiad candidates report being tested on.
  • Write one worked example in Spring Framework and time yourself on it.

Deliverable: One timed worked example in Spring Framework.

Day 4 — Work Object-Oriented Programming (OOP)

  • Spend the session on Object-Oriented Programming (OOP), which Proxiad candidates report being tested on.
  • Write one worked example in Object-Oriented Programming (OOP) and time yourself on it.

Deliverable: One timed worked example in Object-Oriented Programming (OOP).

Day 5 — Answer out loud: Java & Core Development

  • Answer aloud, timed: Explain the difference between object-oriented programming and functional programming in Java.
  • Answer aloud, timed: How does multithreading work in Java, and how do you prevent race conditions?

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

Day 6 — Answer out loud: Enterprise Frameworks & Databases

  • Answer aloud, timed: Explain the core concepts of the Spring Framework, including Dependency Injection and Aspect-Oriented Programming (AOP).
  • Answer aloud, timed: What is the difference between Spring Boot and the standard Spring Framework?

Deliverable: Spoken answers to 2 reported Enterprise Frameworks & Databases question(s), under time.

Day 7 — Answer out loud: Algorithms & Architecture

  • Answer aloud, timed: Walk through the time and space complexity of common sorting and searching algorithms.
  • Answer aloud, timed: How would you design a scalable microservices architecture for a high-traffic client platform?

Deliverable: Spoken answers to 2 reported Algorithms & Architecture question(s), under time.

Behavioural preparation

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

How do you handle database indexing and query optimization to prevent performance bottlenecks?

Medium · Enterprise Frameworks & Databases

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?

Walk me through your professional background and highlight a project where you had to solve a highly complex t

Medium · Behavioral & Consulting Fit

Walk me through your professional background and highlight a project where you had to solve a highly complex technical challenge.

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?

Why are you interested in joining Proxiad as a consultant rather than working for a product-focused company?

Medium · Behavioral & Consulting Fit

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 time when you received constructive feedback on your code. How did you handle it?

Medium · Behavioral & Consulting Fit

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?

What are your professional strengths and weaknesses, and how do you work to improve your technical skills?

Medium · Behavioral & Consulting Fit

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?