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Viasat Software Engineer Interview Guide

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

The 60-second brief

A Software Engineer at Viasat sits at the intersection of cutting-edge aerospace systems, global telecommunications, and high-performance cloud computing. Unlike traditional software companies, Viasat designs and operates massive satellite constellations, ground stations, and secure communication networks that connect commercial airlines, maritime fleets, defense forces, and remote communities worldwide. As a software engineer, you will write the mission-critical code that powers these complex ecosystems, directly impacting how millions of users access secure, high-speed connectivity. The impact of this role is exceptionally broad. You might find yourself optimizing real-time data streaming protocols to reduce latency over satellite links, designing secure APIs for tactical defense communication systems, or scaling the distributed cloud services that manage ground station telemetry.

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

Focus areas

  • Data Structures
  • DSA (Data Structures and Algorithms)
  • Algorithms

The Viasat interview process

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

Recruiter Screen

Initial screening call to evaluate candidate's background and fit for the role.

What to demonstrate

  • Initial screening call to evaluate candidate's background and fit for the role
  • Depth in Data Structures

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.

Technical Phone Interview

In-depth technical interview with a hiring manager or senior engineer.

What to demonstrate

  • In-depth technical interview with a hiring manager or senior engineer
  • Depth in Data Structures

How to prepare

  • Answer aloud and timed: What is IP subnetting, and how do you calculate a subnet mask for a given IP address?
  • Answer aloud and timed: Explain the difference between IPv4 and IPv6 addressing.

Panel Interview

Comprehensive multi-round interview with team members, managers, and system architects.

What to demonstrate

  • Comprehensive multi-round interview with team members, managers, and system architects
  • Depth in Data Structures

How to prepare

  • Answer aloud and timed: How do DNS and HTTP protocols operate over the internet? Describe the complete HTTP request-response cycle.
  • Answer aloud and timed: How do routing protocols like OSPF or BGP gather and distribute routing information?

Where candidates lose points

Master Your Resume

Do not list any technology, framework, or language on your resume unless you can discuss it in detail. Viasat interviewers will pick specific projects from your resume and ask deep, probing questions about your implementation choices and the challenges you faced.

Be Ready for Networking Questions

Regardless of the specific software role, brush up on your networking basics. Knowing the difference between TCP and UDP, understanding how IP addressing works, and being able to explain the OSI model will immediately set you apart.

Ask Thoughtful Questions

At the end of every interview, you will have time to ask questions. Use this opportunity to show your genuine interest in the company's technology and culture. Ask about the team's current technical challenges, how they handle satellite latency, or what the day-to-day workflow looks like.

Questions & practice

Given an array with duplicate values, how would you efficiently filter out the duplicates to optimize memory u

Medium · Data Structures, Algorithms & Coding

Given an array with duplicate values, how would you efficiently filter out the duplicates to optimize memory usage? Discuss the trade-offs between time and space complexity.

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?

Implement both a Depth-First Search (DFS) and a Breadth-First Search (BFS) algorithm for graph traversal. In w

Medium · Data Structures, Algorithms & Coding

Implement both a Depth-First Search (DFS) and a Breadth-First Search (BFS) algorithm for graph traversal. In what real-world scenarios is BFS preferred?

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?

Explain how a Hash Map works under the hood. How do you handle collisions, and what is the worst-case time com

Medium · Data Structures, Algorithms & Coding

Explain how a Hash Map works under the hood. How do you handle collisions, and what is the worst-case time complexity?

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 do you detect if a string contains duplicate elements using a straightforward, optimal approach?

Medium · Data Structures, Algorithms & Coding

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?

Explain the concepts of multi-threading, concurrency, and deadlocks. How do you prevent deadlocks in a multi-t

Medium · Data Structures, Algorithms & Coding

Explain the concepts of multi-threading, concurrency, and deadlocks. How do you prevent deadlocks in a multi-threaded application?

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 a situation where you had to work with ambiguous requirements. How did you structure your approach to

Medium · Behavioral & Leadership

Describe a situation where you had to work with ambiguous requirements. How did you structure your approach to deliver a successful outcome?

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?

Hold a per-tenant active cap against concurrent creates

Hard · write skew · isolation levels · constraints

A tenant on the standard plan may hold at most 50 resources with status='active'. The create handler runs SELECT count(*) FROM resource WHERE tenant_id = $1 AND status = 'active', compares to 50, then inserts. Two creates arrive 3 ms apart on different instances and the tenant lands at 51. Name the anomaly, say whether PostgreSQL 16 READ COMMITTED or REPEATABLE READ prevents it and why, then give an implementation that holds the cap at READ COMMITTED with the exact statements. Finally, say what changes when the cap is 'at most one running export per tenant' on job_run.

Approach

  1. Name it: write skew. The two transactions read an overlapping set and write disjoint rows, so there is no row-level conflict for the engine to detect and each commit is individually legal.
  2. Rule out the levels precisely. READ COMMITTED takes a fresh snapshot per statement and takes no lock on the counted rows, so both see 49. PostgreSQL's REPEATABLE READ is snapshot isolation: it removes non-repeatable reads and phantoms within the snapshot but still admits write skew, because the anomaly is not a re-read of a changed row, it is a read of a set that a concurrent transaction invalidates. Only SERIALIZABLE closes it, by tracking the read dependency and aborting one transaction with SQLSTATE 40001 — a guarantee that exists only if the application re-runs the whole transaction from the read.
  3. Convert the set predicate into a single-row conflict: keep tenant.active_resource_count and run UPDATE tenant SET active_resource_count = active_resource_count + 1 WHERE tenant_id = $1 AND active_resource_count < 50 in the same transaction as the INSERT. Zero affected rows is the cap, returned as 409. The row lock serialises the decision at any isolation level, and contention is bounded to one tenant's row — which is also the fair-scheduling unit, unlike a global counter that would convoy every tenant behind one row.
  4. State the cost you just took on: a counter is a second source of truth that can drift, so every path that changes status must adjust it inside the same transaction, and a periodic reconciliation has to exist, with resource_revision as the authority for what the count should have been.

Follow-up

  • A resource moves from archived back to active. Which statements change, and what breaks if the counter update and the status change land in different transactions?
  • The cap becomes plan-dependent and a plan can change mid-month. Where does the number 50 live, and who reads it?

Keep soft-deleted accounts from blocking re-registration

Easy · soft delete · unique constraints · engine differences

app_user holds user_id, tenant_id, email CITEXT, password_hash (NULL for SSO principals), email_verified_at, auth_version, status ('invited','active','suspended','deactivated'), created_at, updated_at, deleted_at. Two live accounts for one address inside a tenant must be impossible, but an address freed by a soft delete must be reusable, and the same tenant may delete and re-register it repeatedly. Write the uniqueness DDL for PostgreSQL 16, then the equivalent for MySQL 8 where partial indexes do not exist, and say what each permits once three deleted rows already hold that address.

Approach

  1. Start from what is actually unique: not (tenant_id, email), but (tenant_id, email) among live rows. PostgreSQL says that directly — CREATE UNIQUE INDEX app_user_live_email ON app_user (tenant_id, email) WHERE deleted_at IS NULL. A full constraint over the same two columns burns the address permanently the first time someone deletes an account.
  2. Keep case-insensitivity in the type or the index, never in the application: CITEXT as given, or UNIQUE (tenant_id, lower(email)) as an expression index where the extension is unavailable. A case-sensitive unique column is exactly how two accounts for one human appear.
  3. For MySQL 8 the predicate has to move inside the key: add a discriminator column that is a constant 0 while the row is live and is set to user_id on delete, with UNIQUE (tenant_id, email, deleted_marker). Live rows share the constant and still collide; deleted rows differ from each other and stop colliding.
  4. State the NULL variant and its dependency: leaving the marker NULL for deleted rows also works, because a unique index treats NULLs as distinct — true in MySQL, and true in PostgreSQL only under the default NULLS DISTINCT, which PostgreSQL 15 lets you reverse. Check the polarity against the three existing deleted rows: constant-on-live is what preserves the collision you want, and reversing it silently admits duplicate live accounts.

Follow-up

  • A deleted account re-registers with the same address the next day. Do the old resource rows follow the new user_id, and how does the API keep the two principals apart?
  • How do you honour an erasure request while resource_revision.actor_user_id still references this table?

Explain the primary differences between TCP and UDP. In what scenarios would you choose one over the other for

Medium · Computer Networks & Systems

Explain the primary differences between TCP and UDP. In what scenarios would you choose one over the other for satellite data transmission?

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?

Walk me through the layers of the OSI model. How does data flow from the transport layer down to the physical

Medium · Computer Networks & Systems

Walk me through the layers of the OSI model. How does data flow from the transport layer down to the physical layer?

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 IP subnetting, and how do you calculate a subnet mask for a given IP address?

Medium · Computer Networks & Systems

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 difference between IPv4 and IPv6 addressing.

Medium · Computer Networks & Systems

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 do DNS and HTTP protocols operate over the internet? Describe the complete HTTP request-response cycle.

Medium · Computer Networks & Systems

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 do routing protocols like OSPF or BGP gather and distribute routing information?

Medium · Computer Networks & Systems

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?

Walk me through a complex project on your resume. Why did you choose your specific technology stack, and what

Medium · Resume Deep Dive & System Design

Walk me through a complex project on your resume. Why did you choose your specific technology stack, and what was the most difficult technical challenge you overcame?

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?

If you worked on a team-based project, what was your specific role? How did you collaborate with others to ens

Medium · Resume Deep Dive & System Design

If you worked on a team-based project, what was your specific role? How did you collaborate with others to ensure the project's success?

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 the design of a payment gateway integration you implemented. How did you handle third-party API failur

Medium · Resume Deep Dive & System Design

Explain the design of a payment gateway integration you implemented. How did you handle third-party API failures?

Approach

  1. Say who the caller is and what they do when the call fails halfway.
  2. Define the identity of a request so a retry cannot double-apply it.
  3. Separate accepted, pending, failed and confirmed; they are different facts.
  4. Design the error taxonomy before the success shape; callers branch on it.

Follow-up

  • What happens if the caller retries after a timeout?
  • How does a client discover it is on an old version of this contract?

How would you design a server architecture to handle real-time routing data from multiple ground stations?

Medium · Resume Deep Dive & System Design

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 customer endpoint stalls deliveries to every other destination

Medium · bulkhead · timeouts · saturation

The egress service delivers about 1.5k webhooks/second across 40,000 destinations, with a per-destination concurrency cap of 4 and a 10-second connect-plus-read timeout. Throughput falls to 300/second, queue depth climbs, and p99 delivery latency for unaffected destinations goes from 200 ms to minutes, while the error rate barely moves. One tenant holds 900 destination rows whose URLs share a hostname that now answers in 9.5 seconds. Explain the mechanism with the arithmetic, then give the containment in the order you would apply it.

Approach

  1. Look at saturation before errors. A flat error rate with collapsing throughput says nothing is failing, things are waiting, so the first signal to pull is in-flight request count or pool wait time rather than the error counter. This is the distinction that decides the whole investigation.
  2. Group in-flight work by resolved host, not by destination id. The cap is keyed per destination row, so 900 rows sharing one hostname buy 3,600 concurrent slots against a single host, each held for 9.5 seconds. The bulkhead was never a bulkhead for that host, and grouping by the wrong dimension is why the dashboard looked healthy.
  3. Do the arithmetic in both directions. Required concurrency is arrival rate times latency, so 1.5k/second at 200 ms needs about 300 in flight, which is entirely consumed by 3,600 slow slots; conversely whatever concurrency is left sustains rate equals concurrency divided by 9.5 seconds, which is the 300/second you are seeing. Matching both numbers is what promotes this from a plausible story to the mechanism.
  4. Explain why the circuit breaker never helped. It opens on consecutive failures, and a 9.5-second response inside a 10-second timeout is a success. Slow is not failing, so an error-rate breaker cannot see this; you need a slow-call ratio, a deadline propagated from the caller's remaining budget, or a concurrency limiter.

Follow-up

  • The host recovers to 80 ms. How long does the queue take to drain, and what does the drain do to the recovered host?
  • Where should the 10-second timeout number actually come from?

Suggested practice checklist

Built from the rounds and topics Viasat candidates report.

Day 1 — Map the Viasat loop

  • Write out the reported sequence: Recruiter Screen, Technical Phone Interview, Panel Interview.
  • 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 3 reported rounds, with the weakest marked.

Day 2 — Work Data Structures

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

Deliverable: One timed worked example in Data Structures.

Day 3 — Work DSA (Data Structures and Algorithms)

  • Spend the session on DSA (Data Structures and Algorithms), which Viasat candidates report being tested on.
  • Write one worked example in DSA (Data Structures and Algorithms) and time yourself on it.

Deliverable: One timed worked example in DSA (Data Structures and Algorithms).

Day 4 — Work Algorithms

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

Deliverable: One timed worked example in Algorithms.

Day 5 — Answer out loud: Computer Networks & Systems

  • Answer aloud, timed: Explain the primary differences between TCP and UDP. In what scenarios would you choose one over the other for satellite data transmission?
  • Answer aloud, timed: Walk me through the layers of the OSI model. How does data flow from the transport layer down to the physical layer?

Deliverable: Spoken answers to 2 reported Computer Networks & Systems question(s), under time.

Day 6 — Answer out loud: Data Structures, Algorithms & Coding

  • Answer aloud, timed: Given an array with duplicate values, how would you efficiently filter out the duplicates to optimize memory usage? Discuss the trade-offs between time and space complexity.
  • Answer aloud, timed: Implement both a Depth-First Search (DFS) and a Breadth-First Search (BFS) algorithm for graph traversal. In what real-world scenarios is BFS preferred?

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

Day 7 — Answer out loud: Resume Deep Dive & System Design

  • Answer aloud, timed: Walk me through a complex project on your resume. Why did you choose your specific technology stack, and what was the most difficult technical challenge you overcame?
  • Answer aloud, timed: If you worked on a team-based project, what was your specific role? How did you collaborate with others to ensure the project's success?

Deliverable: Spoken answers to 2 reported Resume Deep Dive & System Design question(s), under time.

Behavioural preparation

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

For hardware-adjacent roles: Describe your experience with FPGAs, SystemVerilog, or analyzing components like

Medium · Resume Deep Dive & System Design

For hardware-adjacent roles: Describe your experience with FPGAs, SystemVerilog, or analyzing components like capacitors and inductors.

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?

Tell me about a time you had a conflict with a teammate or classmate. How did you resolve it, and what did you

Medium · Behavioral & Leadership

Tell me about a time you had a conflict with a teammate or classmate. How did you resolve it, and what did you learn from the experience?

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 is your proudest technical achievement, and why does it stand out to you?

Medium · Behavioral & Leadership

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 do you want to work for Viasat, and how do you see your skills aligning with our mission to connect the wo

Medium · Behavioral & Leadership

Why do you want to work for Viasat, and how do you see your skills aligning with our mission to connect the world?

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?