Arista

Large Enterprises

Arista Networks is a computer networking company that designs and sells multilayer network switches and software for large-scale data centers, cloud computing, and enterprise environments. It is known for its high-performance switches and its EOS (Extensible Operating System) network operating system, and is a major competitor to Cisco in the data center networking market.

5 interview notes · updated Jul 2026

Arista·Software Engineer·Technical Phone Screen

Jul 2026

Arista software engineer interview with a C/C++ debugging question that had a sneaky follow-up I wasn't fully ready for.

You're given a C or C++ snippet with a bug caused by out-of-bounds memory access. Identify the bug and explain why it's unsafe.
Given that invalid memory access usually causes a segfault, why might this particular program instead run indefinitely and appear to loop forever?

“Pretty standard stuff if you've done any low-level C work.”

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Arista·Software Engineer·Technical Phone Screen

Jun 2026

Did a coding round for a Software Engineer role at Arista. One question, linked list manipulation, nothing flashy but it required some care to get right in-place.

Given the head of a singly linked list and a target integer, remove all nodes with that value and return the updated head. Do it in-place, no auxiliary list.

“Seems straightforward until you realize the head itself might need to be removed.”

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Arista·Software Engineer·Technical Phone Screen

Jun 2026

Arista software engineer interview with a binary search problem that looks straightforward until you actually sit down and think about the edge cases. The O(log n) constraint is what makes it interesting.

Given a sorted array of distinct integers that should form a consecutive sequence (possibly starting at any integer), find the one missing number if it exists, or return null if nothing is missing. Must run in O(log n) time and O(1) space.

“My first instinct was to just compute the expected sum and subtract, which is O(n) and they shut that down immediately.”

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Arista·Software Engineer·Technical Phone Screen

Jun 2026

Coding interview for a software engineer role at Arista. Two problems, both with complexity analysis required. Nothing too wild but the binary search follow-up on the second problem is where things get interesting.

Write a function to check if a string is a palindrome. Handle null input and treat an empty string as a valid palindrome.
Given a sorted array of distinct integers forming a consecutive sequence with exactly one missing number (sequence doesn't necessarily start at 0), find the missing number. First explain an O(n) solution, then optimize to O(log n) using binary search.

“Pretty standard.”

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Arista·Software Engineer·Technical Phone Screen

May 2026

Technical phone screen for a software engineer role at Arista, heavy on C fundamentals and memory model questions. Pretty low-level stuff, felt like they wanted to see if you actually understood what the compiler and OS are doing under the hood.

Given `const char *c = "12345"`, what does each of these printf calls actually do: `printf("%s", c)`, `printf("%d", c)`, `printf("%c", c)`, `printf("%c", *c)`, `printf("%c", *(c+1))`, and what's the correct way to print the address stored in `c`?
How would you use gdb or lldb to inspect the pointer value of `c`, the raw bytes at that address, and the string stored there?
Compare malloc/free versus new/delete in C and C++, covering initialization behavior, constructor and destructor calls, type safety, failure handling, and array variants.
What typically lives in the stack, heap, data segment, BSS segment, and text segment? Where does a string literal like "12345" end up?

“The %s and %c with dereference cases were fine, but I fumbled on %d and %c with c directly.”

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