Arista Networks interview process (2026)
Round-by-round breakdown of the Arista Networks software engineering interview across 3 levels and 13 rounds: what each round covers, what interviewers evaluate, sample questions, and preparation tips.
Software Engineer (New Grad / Campus)
Difficulty: Hard · Timeline: ~2-4 weeks · Recommended prep: 8-10 weeks · Cooldown: ~6 months
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Round 0: HackerRank Online Assessment
Assessment · ~90 min · difficulty 3/5 · elimination round
Focus: DSA coding in C/C++, CS-core MCQs (OS, CN, DBMS, C output questions)
HackerRank test, typically ~15 MCQs on OS/CN/DBMS/C plus 2-3 coding problems (reported set: BFS shortest path with obstacles, message aggregation and sorting, an interval-merge variant). Campus reports show a hard cut: roughly 11 of 40 candidates cleared by solving at least 2 of 3 problems. C and C++ are the expected languages.
What they evaluate: Whether you can solve LeetCode-medium problems fast in C/C++ and whether your CS fundamentals (memory layout, processes vs threads, TCP basics) are solid enough for the onsite rounds.
Sample question: Shortest path in a grid — given an R x C grid of 0s and 1s (1 = obstacle), print the minimum number of 4-directional moves from the top-left to the bottom-right cell, or -1 if unreachable. Input: R C, then the grid rows. Reported in Arista's campus OA as a BFS-with-obstacles problem.
Tips: Do timed C++ practice on HackerRank specifically — the editor has no autocomplete crutches. Revise C output-style MCQs (pointer arithmetic, operator precedence, storage classes); they decide ties.
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Round 1: Technical Interview 1 — DSA from scratch in C/C++
Onsite · ~60 min · difficulty 4/5 · elimination round
Focus: Linked lists, stacks, tries, recursion vs iteration, C memory layout
Google Meet with a shared plain editor — no IDE, no autocomplete, and no STL: you define the node struct, allocate memory and do the pointer surgery yourself. Reported questions: rearrange/reverse linked lists, design a stack, a Zomato-like restaurant search built on a trie, bitonic array search. Interviewers also drop in C questions mid-problem: static vs global, where variables live, x++ vs ++x debugging.
What they evaluate: Clean pointer manipulation without a safety net — null checks, no leaks, correct edge cases — plus whether you actually understand what the machine does (stack vs heap, recursion cost).
Sample question: Reverse a singly linked list in groups of k — define the node struct yourself, build the list from input, and reverse every group of k nodes in place using only raw pointers (no STL). Input: n k, then n values; print the resulting list. It is highly probable you get one linked-list or tree question in this round.
Tips: Practice writing whole tree/linked-list programs from scratch — struct, build, operate, free — until you can do it without thinking. Narrate your pointer updates; interviewers here care that the code would survive a code review (no leaks, handle null).
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Round 2: Technical Interview 2 — C/C++ internals, memory and OS
Onsite · ~60 min · difficulty 4/5 · elimination round
Focus: Pointers, malloc/free, struct padding, varargs, bit manipulation, processes vs threads, mutex/semaphore
The signature Arista round: language internals, not algorithms. Reported questions: implement your own printf with format strings and varargs; what does int *x[N] declare; why sizeof(struct) exceeds the sum of members (padding) and the struct hack; const pointers vs pointers-to-const; O(1) bit tricks; test-and-set, locks and mutexes on a multiprocessor; debugging a buggy pointer program live. Note: even when the JD says C++, several teams (especially EOS) effectively interview in C.
What they evaluate: Depth in C — can you explain and code what malloc, the linker and the compiler actually do. Hand-wavy answers end the round; they probe until you hit the edge of your knowledge.
Sample question: Implement my_printf(const char* fmt, ...) using <cstdarg> supporting %d, %s and %c, writing characters with putchar only. Follow-ups: what does int *x[10] declare vs int (*x)[10]; why can sizeof a struct exceed the sum of its members; how does the struct hack / flexible array member work?
Tips: Reread the pointers/memory chapters of a C book (K&R or Deep C Secrets level) — this round is won there, not on LeetCode. Say the invariant out loud before coding (alignment, promotion rules for varargs) so partial credit lands even if you slip on syntax.
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Round 3: Technical + HR wrap-up
Behavioral · ~60 min · difficulty 2/5
Focus: CS-fundamentals sweep, projects, motivation, team fit
Combined closer with a senior engineer or manager: light technical sweep of anything not yet covered (how would you implement a HashMap, virtual memory basics, favourite subjects, internship projects) plus standard HR — why Arista, why networking systems, Pune vs Bengaluru preference. No HLD system design is asked at this level; campus reports show all finalists who reached this round getting offers.
What they evaluate: Consistency with earlier rounds, genuine interest in low-level systems work, and communication. This round rarely eliminates but sloppy fundamentals here can still sink a borderline candidate.
Tips: Have a crisp story for why you want systems/networking work rather than generic product dev — Arista filters hard for that motivation. Know your resume projects down to the design decisions.
Software Engineer (Experienced, 3-6 yrs)
Difficulty: Hard · Timeline: ~2-4 weeks · Recommended prep: 6-8 weeks · Cooldown: ~6 months
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Round 0: Recruiter screen
Phone · ~30 min
Focus: Background, C/C++ depth check, team matching (EOS, SONiC, hardware, tooling), logistics
Recruiters (often via LinkedIn outreach for Pune/Bengaluru) walk your background and set expectations explicitly: the loop is very technical and C/C++ heavy, fundamentals over frameworks. Candidates are warned that even if the role says C++, some teams — especially EOS — will interview largely in C.
What they evaluate: Years of real C/C++ (not just college C++), systems exposure (Linux, networking), and which team pipeline fits you.
Tips: Ask which team the loop is for — EOS vs SONiC vs tooling changes what to prep (pure C and kernel vs open-source networking vs Python). Be honest about your C++ level; the rounds will find it anyway.
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Round 1: Coding round — 3 problems, live C++ on CoderPad
Onsite · ~60-75 min · difficulty 4/5 · elimination round
Focus: Kadane, stack design, tries, arrays; mandatory C++, code must actually run
A CoderPad marathon: one reported loop asked Maximum Subarray (Kadane, O(N) required), design a stack with O(1) getMin, and a phone-number autocomplete built on a trie — all coded live in C++ and debugged until they executed. No STL for the data-structure problems: you write the node structs yourself. Interviewers interleave malloc/pointer questions while you code.
What they evaluate: Speed with correctness across multiple problems, from-scratch data-structure implementation, and composure while debugging your own code in front of the interviewer.
Sample question: Design a stack supporting push, pop, top and getMin all in O(1) — implement it from scratch in C++ without STL containers (write your own linked node struct), then process q operations read from stdin and print answers for top and min queries (print "empty" when the stack is empty).
Tips: Practice tries, stacks and heaps from scratch in C++ before this round — Arista explicitly expects implementations, not container calls. Keep a mental malloc story ready: reports show candidates getting grilled on allocation mid-problem.
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Round 2: C/C++ internals and OS deep dive
Onsite · ~60 min · difficulty 5/5 · elimination round
Focus: STL internals in C, LRU from scratch, skip lists, concurrency primitives, memory model
The round Arista is famous for. Reported questions: implement std::vector in plain C (growth policy, realloc semantics); implement an LRU cache from scratch (doubly linked list + your own hash map); make linked-list search faster than O(n) with skip lists; running mean/median over a stream; test-and-set vs mutex vs semaphore with multiprocessor constraints; struct padding and the struct hack; sorting data larger than RAM. All on a plain shared editor, no STL allowed for the core structures.
What they evaluate: Whether you understand the machinery you use daily — allocators, cache behaviour, synchronisation — deeply enough to rebuild it. This is the primary hire/no-hire signal for experienced candidates.
Sample question: Implement an LRU cache from scratch: doubly linked list plus your own hash table (no std::unordered_map), get and put in O(1). Follow-ups: how would you implement std::vector in C — growth factor, realloc vs malloc+memcpy, amortised cost — and when does test-and-set beat a mutex on a multiprocessor?
Tips: Rebuild vector, unordered_map, shared_ptr and an LRU in C/C++ from memory before the loop — these exact asks recur across years of reports. When stuck, reason from the memory layout; interviewers reward first-principles thinking over memorised answers.
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Round 3: Networking / systems round with live C debugging
System_design · ~90-120 min · difficulty 4/5 · elimination round
Focus: TCP/IP, L2/L3, VRF, TCAM, ACLs, Linux namespaces, eBPF (team-dependent), memory-safety debugging
For networking-adjacent teams (SONiC, EOS): a long, deep session — one 2024-25 report ran nearly 2 hours with a US-based SONiC engineer. Topics: packet walk through a switch (L2 lookup, VLAN, route lookup, TCAM/ACL, MAC rewrite), VRFs, ASIC-level concepts, then a hands-on segment building a multi-hop topology with Linux network namespaces and a live C debugging task hunting memory-safety bugs. This is low-level design close to the metal, not classic HLD boxes-and-arrows.
What they evaluate: Real networking depth (not just OSI-layer recitation), Linux fluency, and disciplined debugging — one candidate was marked down simply for spraying printf inside a loop instead of reasoning first.
Sample question: On one Linux machine, use network namespaces and veth pairs to build a 3-hop topology and make end-to-end ping work. Then walk a packet through a switch: L2 MAC lookup, VLAN handling, L3 route lookup, TCAM/ACL processing and MAC rewrite — where does each step run in hardware vs software?
Tips: Lab this on your own laptop beforehand: ip netns, veth, ip route — muscle memory shows. When handed buggy C, read it fully and state hypotheses before touching it; composure under debugging is explicitly scored.
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Round 4: Hiring manager round
Behavioral · ~45-60 min · difficulty 2/5
Focus: Project deep dive, debugging war stories, why Arista, offer discussion
Conversation with the hiring manager: deep dive into your most complex project, how you debug production issues, why you want switch/OS-level work, and team/location fit (Pune vs Bengaluru). Compensation discussion follows this round; India candidates report the offer stage can involve multiple approval back-and-forths, so pin numbers down in writing.
What they evaluate: Ownership, debugging maturity, and genuine systems motivation. Managers probe whether you will thrive in a low-tooling, high-autonomy C/C++ codebase.
Tips: Bring one production-debugging story with a kernel/network/memory angle and tell it with specifics (tools, hypothesis, fix). Get any verbal comp commitment reflected in the written offer before resigning anywhere.
Senior Software Engineer
Difficulty: Hard · Timeline: ~1-2 weeks · Recommended prep: 4-6 weeks · Cooldown: ~6 months
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Round 0: Recruiter screen
Phone · ~20 min
Focus: Background, motivation, level calibration, logistics
Short call covering background and motivation. Arista's senior loop in India moves unusually fast — one Bengaluru candidate went from first recruiter contact to offer in a single week. Expect the loop to be compressed into back-to-back sessions.
What they evaluate: Seniority calibration and whether your systems background merits the fast-tracked loop.
Tips: Because the loop moves fast, be interview-ready before you say yes — there may be only days between the screen and the technical rounds.
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Round 1: Coding + fundamentals with a senior engineer
Onsite · ~60 min · difficulty 4/5 · elimination round
Focus: Pointer-heavy coding twist, concurrency (CAS, atomics, volatile), language runtime internals
One coding problem with a twist plus fundamentals. A reported Bengaluru question: reverse a linked list in groups of k where k follows the Fibonacci sequence. Concurrency follow-ups probe volatile, atomic variables vs synchronized/locks, CAS operations and a thread-safe singleton. Coding happens in a plain shared editor; for C++ roles expect raw-pointer implementations without STL, and for platform teams the discussion can pivot to whichever runtime you claim depth in.
What they evaluate: Production-quality code under a novel constraint, plus genuine concurrency understanding — seniors are expected to reason about memory visibility and lock-free primitives, not just name them.
Sample question: Reverse a singly linked list in groups whose sizes follow the Fibonacci sequence (groups of 1, 1, 2, 3, 5, ...), in place with raw pointers and no STL. Follow-ups: what does volatile actually guarantee, when do atomics with CAS beat a mutex, and how do you write a thread-safe singleton?
Tips: Solve the standard reverse-in-k-groups first, then generalise the group size — interviewers watch how you adapt a known pattern. Refresh the C++ memory model (or JMM) enough to explain CAS loops precisely.
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Round 2: Systems design with the engineering manager
System_design · ~60-90 min · difficulty 4/5 · elimination round
Focus: Low-level design of a messaging/email system, OS-level reasoning, hands-on CLI/regex task
Design at the process-and-memory level rather than boxes-and-arrows HLD: a reported prompt was the backend of an email/messaging system — storage layout, delivery pipeline, failure handling — followed by a hands-on task building a small command-line tool with regex pattern matching. For networking teams this round instead goes deep on packet paths, VRF/TCAM/ACL behaviour and Linux internals. Concurrency in multiprocessor environments (as in the URL-shortener variant asked on campus) is a recurring thread.
What they evaluate: Whether your design instincts extend down to syscalls, file layout and memory — Arista seniors own features end to end through the EOS/SONiC stack, so shallow web-scale architecture answers do not land.
Sample question: Design the backend of an email/messaging system at the process level: on-disk storage layout, delivery pipeline, retry and failure handling, and how concurrent readers/writers stay safe on a multiprocessor. Then: sketch a CLI tool that filters a large log file with a regex — what are its memory and I/O characteristics?
Tips: Anchor every design choice in OS mechanics (page cache, fsync, mmap, epoll) — that vocabulary is the pass signal here. Practice one hands-on task end to end: parse args, stream a file, apply a regex, measure it.
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Round 3: Director conversation + fit
Behavioral · ~45 min · difficulty 2/5
Focus: Language/runtime internals conversation, debugging philosophy, leadership and fit
Conversational final with a director/site leader: reported topics include the deepest difference between managed and unmanaged languages (GC vs manual memory), how memory leaks arise even under GC, how you approach debugging gnarly production issues, and what you want from Arista's flat, small-team engineering culture in Pune/Bengaluru.
What they evaluate: Technical judgment at conversational depth, self-directedness, and culture fit for small senior teams with minimal process. A weak conversation here can still lose an otherwise strong loop.
Tips: Prepare a first-principles answer on memory management across languages — it is a reported favourite. Ask sharp questions about EOS architecture; curiosity about the product is read as strong signal.
Other companies' interview processes
Worked sample solutions (code, design diagrams, and STAR answers) for every round are available in the FAANGPlus app: open interview processes.