Meta software engineer interviews: code clearly and explain your checks

Practice the reasoning behind your code, not a collection of memorized answers. Start with a small counting problem, explain why your approach works, then test the cases that could expose an incorrect assumption.

Try three original practice questions

Original Prepti practice, not real or reported employer questions. Optional timing is a practice aid, not an employer test limit. No score prediction or account needed.

Try it: 3 original questions on frequency and countingUntimed

Original Prepti practice, not employer questions. Timing is optional; no answer is submitted automatically.

JavaScript is off. Read the original questions and worked answers below; no timer is required.

What does first_unique(“aabccde”) return?

def first_unique(s):
    counts = {}
    for ch in s:
        counts[ch] = counts.get(ch, 0) + 1
    for idx, ch in enumerate(s):
        if counts[ch] == 1:
            return idx
    return -1

2: The first pass counts; the second pass scans in string order, so it returns the leftmost character seen once – 'b' at index 2. A test case worth keeping: "aabb" must return -1 (no unique character at all), which catches versions that forget the -1 path.

How many unordered index pairs (i < j) in a = [1, 2, 2, 3, 1] sum to k = 4?

# Counting with a frequency map:
# pairs of value 1 with value 3: count(1) * count(3)
# pairs of value 2 with value 2: C(count(2), 2)

3: 1s sit at indices 0 and 4, the 3 at index 3: that gives 2 pairs. The two 2s form 1 pair. Total 3. The duplicate-heavy test case [2, 2] with k = 4 is the one that breaks sloppy solutions: it must count exactly 1 pair and must never use the same element twice.

How many groups does an anagram grouper produce for the input below?

group_anagrams(
  ["eat", "tea", "tan", "ate", "nat", "bat"]
)

3: With sorted letters as the key, "eat"/"tea"/"ate" share one key, "tan"/"nat" share a second, and "bat" stands alone – 3 groups. Edge test cases that matter: an empty input list returns 0 groups, and words of different lengths can never share a key.

What the official Meta software engineering guide covers

Meta’s software engineering preparation page links to a Full Loop Interview Guide written by its engineers and recruiters. The linked PDF describes four to six interviews of 45 minutes and names coding, design and behavioral interviews. That is the scope of the guide, not a universal promise about every candidate’s schedule. Your recruiter confirms your actual loop.

The coding section emphasizes your solution, the structure and style of your code, and narration of your thought process. It says the interviewer will not compile the code in the format described there, and asks you to confirm coding-language preferences with your recruiter. Do not turn that into a rule for every newer tool-assisted interview: Meta’s current general hiring page separately describes authorized AI assistants in some technical interviews.

The guide’s design section distinguishes systems and product-oriented design. The appropriate preparation depends on the interview your recruiter assigns. This page does not provide real or candidate-reported Meta questions.

Try an original Meta preparation exercise

The three questions below use frequency counting, duplicated values and meaningful tests. They are original Prepti teaching exercises, not employer assessment items. The optional timer gives you a short practice window, not a predicted Meta time limit or score.

Explain a frequency-counting solution

Suppose your task is to count how often each identifier occurs in an input list. First clarify whether identifiers are case-sensitive and whether the input may be empty. A map from identifier to count lets you update one entry for each input item, then inspect the resulting counts.

Under the usual average-case hash-map assumption, scanning n items takes O(n) work. A map with k distinct identifiers uses O(k) extra space. State the assumption rather than promising every operation has a worst-case constant cost in every implementation.

Do not sort the original input silently if the task requires it to remain unchanged. Sorting a copy can be a valid alternative with a different time and memory trade-off. Explain why it fits the requirements rather than treating one data structure as the answer to every problem.

Tests that reveal Meta-practice reasoning gaps

Empty input

What should the function return when nothing appears? Confirm the contract before choosing a placeholder.

Same item repeated

A list such as [A, A, A] checks whether you count occurrences or accidentally keep a presence flag.

One character, different case

[A, a] checks an unstated case-sensitivity assumption. Neither answer is correct until that rule is specified.

After finding a bug, explain the assumption that caused it, make the smallest relevant change, and rerun a test that would have failed before. Then check the ordinary path still works.

Prepare Meta behavioral evidence without borrowing a story

Choose a real collaboration, disagreement or learning example that is relevant to the vacancy. Explain your own role, how you reached a decision, what happened and the limits of the result. Do not turn a small student project into a large commercial launch, claim a team result as your sole work or invent a user metric.

Use an original reflection prompt

Think of an occasion when a test or a teammate’s observation changed your first explanation of a bug. What did you believe initially? What evidence contradicted it? What did you change? What remained uncertain? This is a Prepti preparation prompt, not a reported Meta question.

The Meta hiring guide includes a truthful-experience builder and preparation routes for the broad recruiting process.

Keep Meta AI permissions round-specific

The current hiring FAQ says many technical interviews include a built-in AI assistant and candidates are expected to use it. It also limits the CoderPad assistant statement to select roles. The linked SWE PDF prohibits unauthorized outside assistance.

Ask which format you have. If an assistant is explicitly provided, practice explaining what you accept, reject and test, rather than treating generated code as evidence of correctness. If it is not provided, do not bring an external assistant. In either format, keep your reasoning and tests visible.

A focused Meta software engineer preparation session

Solve the original counting drill and read each explanation.
Implement a related function in a language you can explain.
Narrate one normal trace and one boundary case.
Explain time and storage with variables tied to the input.
Prepare one real collaboration example and one question for the team.
Review your recruiter-provided design and coding guidance for the actual round.

This is a practice plan, not an employer scoring system. Three multiple-choice questions do not replace deeper coding, design or experience preparation.

Meta software engineer questions

Are there always exactly two coding interviews?

The retrieved official full-loop guide describes four to six interviews across coding, design and behavioral areas. It does not establish one universal count of coding rounds. Confirm your own schedule with your recruiter.

Will my code be compiled?

The linked preparation PDF says no compilation in the coding format it describes. Newer tool-assisted formats are discussed on the current hiring webpage. Confirm which environment applies instead of relying on an older-format assumption.

Are these actual Meta interview questions?

No. The exercises are original Prepti practice with worked explanations. They are not copied, reported, endorsed or calibrated by Meta.

Choose your next practice step

Free reasoning practice Read an assessment invitation Prepare your online assessment setup

Meta hiring process and preparation

Compare other tech-employer preparation

Google hiring preparation Amazon hiring preparation Atlassian engineering interviews Microsoft hiring preparation NVIDIA hiring preparation

Sources and how to use this guide

Employer process statements come from the official sources above. The exercises, examples, practice plans and tools are original Prepti teaching, not employer questions or scoring criteria. Your vacancy, invitation and recruiter determine the actual interview requirements.

By Prepti Team. Last checked: November 9, 2026. Independent preparation; not affiliated with Meta.

Counting check: repeated values are distinct index pairs

Original extension: use the list [2, 2, 2] and target 4. Count unordered pairs of distinct indices, not distinct value pairs. How many exist, and when should a streaming frequency-map solution increment the count?

Reveal the trace and the common bug

The three index pairs are (0,1), (0,2) and (1,2). A left-to-right implementation first adds the count of the complement among earlier entries, then increments the current value’s frequency. Its increments are 0, 1 and 2, totaling 3.

Incrementing the frequency first lets an element pair with itself. Counting only unique value pairs returns one, which answers a different problem. For this contract, an input containing n copies of 2 has n(n-1)/2 valid index pairs.

Test empty input, one element, negative values and duplicates. Keep the meaning of a pair explicit in your spoken answer. Under average-case hash-map assumptions, the one-pass method takes O(n) time and O(k) storage for k distinct values; the number of pairs can require a sufficiently wide integer in fixed-width languages.

Practise member-level data modeling

Original Prepti practice extension, added November 11, 2026. Fictional inputs, not employer questions or scoring rules.