How to Hire Software Engineers: Best and Worst Practices

GayleL. McDowell | Founder/ CEO, CareerCup
gayle in/gaylemcdgayle
Dev Interview Training
How to InterviewDevelopers:Best& WorstPractices
Oct 15, 2015

gayle in/gaylemcdgayleGayle Laakmann McDowell 2
Hi! I’m Gayle LaakmannMcDowell
Author Interview Coach Interview Consulting
<dev> </dev>
(CS) (MBA)

Core Beliefs
Philosophies around hiring
01

Gayle Laakmann McDowell 4gayle in/gaylemcdgayle
#1: Interviews don’tneed to mirror the real world

#2: Goodcandidateexperiences matter

#3: You’llnever have a perfect process

#4: You need to THINK aboutyour process

The Interview
Goals & Questions
02

Goals
Great employees, not great interviewees
Goodin 6months,not 6days
Reduce falsenegatives
Keepcandidates happy 
9

Core Question Types
Experience/Behavioral Questions
Knowledge
Design/Architecture
ProblemSolving/Algorithms
Coding
10
Canbemixedandmatched!

Behavioral/Experi
ence
What do you ask and why?
03

1. Why?
Isthisapersonyouwanttoworkwith?
Technical expertise
 Hasmadegood,interestingtechnicaldecisions
Culturefit/personality
 Notarrogant,curious,initiative,etc
Communication
 Can theyarticulateimpact?

2. BadPractices& FalseNegatives
Undefined“cultural fit”
Interviewerassumptions
Overly specific questions
Not focusing on self
 “We”not“I”

3. Best Practices
Probe deeper
Be nice and friendly
 (Evenifyoufeeldifferently)
Stick to more technicaldiscussions
ChallengeYOUR assumptions
Inevery interview

4. Evaluation
A factor in ALL interviews
Err towards listing minor concerns
 Evenifit’sjusta “feeling”
Challengeyour assumptions

5. Examples
Dive into a technicalproject
 Walk throughdesignonwhiteboard
 Discusstradeoffs,keydecisions,etc
 Extensionstoproject(scaling,etc)
 Focusonpersonalimpact

Knowledge
What do you really need?
04

1. Why?
Do they know the stuffthey should?
Do they have therelevant job skills?

2. Bad Practices& False Negatives
Only basic knowledge
Requiring stuffyou don’t really need
Too many factualquestions

3. Best Practices
Hard to acquire ORa red flag
Relevant to job
Discussions > fact grilling
 Evaluationshouldbemostlyqualitative
 OR:QuestionseasilyGoogledare bad

4. Examples
How does ____ work?
How do you thinkit’s implemented?

1. Why?
Tests:
 Abilitytotackleopen-endedproblems
 Communication/teamworkskills
 Adifferentsideofproblem-solving
Respects experience of senior candidates

2. Bad Practices & False Negatives
Unreasonable knowledgeexpectations
Some candidates don’t know “theflow”
 Can’taskquestions
 More ofa factualanswer
 Don’tdrivetheprocess

3. Best Practices
Ask open-ended problems
Encourage follow up questions
Have candidate walk through
Let candidatedrive

4. Evaluation
Ability to make tradeoffs
Ability to identify issues
Separate knowledge from attributes
Response to feedback

5. Examples
DesignAPI for…
System for Amazon book rank
System for TinyURL
OOD for a music library

Algorithms
Make ‘em think
06

1. Why?
Smart people do good work
Hires adaptable people
Very effectiveifdonewell

2. Bad Practices& False Negatives
Easy questions
Questions with “a ha” moments
Well knownproblems (or patterns)

3. Best Practices
Ask the right questions
Be nice and friendly
Coach
MAKE THEM THINK

3a. The Right Questions
Medium-to-hardquestions
Multiplehurdles
Unusualquestions
Avoid obscure knowledge

3a. ReasonableKnowledge
Data Structures Algorithms Concepts
ArrayLists Merge Sort BigO Time
Hash Tables QuickSort BigO Space
Trees(+Tries) Breadth-FirstSearch Recursion
Graphs Depth-FirstSearch Memoization/ Dynamic
Programming
Stacks/ Queues BinarySearch
Heaps

3b. Be Nice and Friendly
Intimidatedcandidates do poorly
Candidatescling to every word
 Usethis!
 “Goodjob”,“greatpoint”,etc.
Especiallyifthey’restrugglingornervous

3c. Coach
Give hintsas necessary
Encourage examples (input/output)
Remindthem of key details
Stop themfrom writingcode too early

3d. Phone Interviews vs. Onsite
Don’t “go easy” on thephone
But avoid problems needingdiagrams
 Strings,hashtables,linkedlistsare easytodraw
 Treesandgraphsare hard

4. Evaluation
Not just correct vs. incorrect
 Howoptimal?Howquickly?Howmanyhints?
Compare to other candidates
 Earlyonyouwon’tbecalibrated
More of a “gut feel”thana metric

Rand7: Given rand5(), implementrand7()
 Has“aha” moment
5. Bad Questions

Sub Permutations: Given two strings, s and t, find all
permutationsof s withint.
5. Good Question

1. Why?
Code quality matters
Not everyone can translatealgorithm into code

2. Bad Practices & False Negatives
Requiring every detail
Tedious questions
Taking over the testing
Lettingthe candidate code too early

Goal: “Seemingly compilable” code.
Don’t waste time
 Do you really need that Node class?
 Encourage abbreviations, skipping uninteresting parts, etc.
Make it clear when they should/shouldn’t code
Encourage testing, refactoring, etc
3. Best Practices

4. Whiteboardvs. Computer
 More communication
 Morethought
 More focus on essentials
 BUT: slow & tedious
 Can bemore comfortable
 Can write faster
 BUT: compiling can be
distracting

5. Evaluation
Look at structure and style
 Butdifferentiatewhat’strainable
Not about complete vs. incomplete
Let the candidate test

Final Thoughts
Things to remember
07

Remember:
It’s on YOU to get theinfo you want
Challengeyour assumptions
Separate “did they do X?” from “can they do X?”
47

Remember:
Err towards noting iton feedback
Be nice andfriendly
MAKE THEMTHINK
48

THANK YOU
gayle@gayle.com
gayle in/gaylemcdgayle

How to Hire Software Engineers: Best and Worst Practices

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