Incident! Learning from the CrowdStrike Outage: modal perfects for an incident review
About this lesson
Modal perfects like must have and needn't have are taught in this C1 English for IT lesson plan on incident postmortems.
- Grammar
- Modal perfects for looking back (The validator should have rejected the file.), must have vs had to, needn't have vs didn't need to, and narrative tenses for the timeline.
- Topic
- Incident reviews, with the CrowdStrike outage of July 2024 as a blameless case study and words such as root cause, boot loop, slip through and in hindsight.
- Activities
- A case study to read, a postmortem reading club to hear, self-checking drills, a chat and open boxes, then a postmortem section to write and an incident briefing to record.
What's inside
Chapter 1Warm-up: war stories from on-call
Chapter 2Reading: the 78-minute update
Chapter 3Listening: the postmortem reading club
Chapter 4Grammar: what happened vs what should have happened
- Study the scheme: narrative tenses and modal perfectsGrammar schemeTry it
- Choose the correct narrative tense: last Thursday's incidentChoose the optionTry it
- Fill in the gaps with modal perfectsFill in the gapsUnlock
- Choose the correct option: looking back at incidentsChoose the optionUnlock
- Choose the correct answer: what does it mean?QuizUnlock
Chapter 5Speaking: no blame, just facts
Chapter 6Homework: your own postmortem
- Fill in the table: past simple or past participle?Fill in the tableUnlock
- Sort the phrases: cause, impact or recovery?Sort into columnsUnlock
- Write the "What went wrong" section of a blameless postmortemWriting, checked by the teacherUnlock
- Record an incident briefing for the next on-call engineerSpeaking, checked by the teacherUnlock
Vocabulary
10 words and phrases from the lesson, each with a picture and audio in edio.
+7 more with pictures and audio in the lessonMore words
- slip through
- escalate
- wildcard
- boot loop
- page someone
- blameless postmortem
- in hindsight
Grammar: modal perfects and narrative tenses
An incident review has two jobs: tell what happened, then judge what should have happened. Narrative tenses do the first, and modal perfects such as should have caught do the second. With the CrowdStrike outage of July 19, 2024, as the case, learners criticize the process instead of people, speculate, deduce and say when an action wasn't necessary.
Narrative tenses and modal perfects
Tell what happened with narrative tenses. Then look back with modal perfects: what should, could or must have happened.
Telling the incident: narrative tenses
The past simple carries the main events in order: The change went out, errors started and Tom rolled it back. The past continuous sets the background, and the past perfect jumps back only when the order matters: By the time Lena joined, the incident had ended.
Narrative tenses: who does what in the story
| Tense | Form | Use it for | Example |
|---|---|---|---|
| past simple | worked, went | the main events, in order | The change went out, errors started and Tom rolled it back. |
| past continuous | was / were + -ing | the background: an action in progress when something happened | Rui was writing a test when the alert fired. |
| past perfect | had + past participle | an earlier event, when the order matters | By the time Lena joined, Tom had already rolled back the change. |
| past perfect continuous | had been + -ing | an earlier activity that lasted up to that moment | The tests had been passing for weeks, so nobody looked closely. |
Past perfect only when the order matters
Tell events in order with the past simple: the change went out, errors started, Tom rolled it back. Use the past perfect to jump back to something earlier: by the time Lena joined, the incident had ended. With after or before, the order is already clear, so the past simple is enough.
Modal perfects: one form
Every modal perfect has three parts: a modal (should, could, might, must, can't, would, needn't), have, and a past participle: The pipeline should have caught it. The tests can't have checked the 21st value.
should / could / might / must / can't / would / needn'thavepast participle
The pipeline should have caught it.
The tests can't have checked the 21st value.
We needn't have woken the whole team.
What each modal perfect means
Should have criticizes a step that didn't happen, could have names an unused option and might have speculates; must have and can't have are deductions. Would have gives the result in an imagined past: If the file had gone to a canary group first, fewer machines would have crashed.
| Modal perfect | Meaning | Example |
|---|---|---|
| should have + past participle | it was the right thing to do, but it didn't happen | The validator should have rejected the file. |
| shouldn't have + past participle | it happened, but it was a mistake | Our flag changes shouldn't have gone to every server at once. |
| could have + past participle | it was possible, but it didn't happen | A canary stage could have caught it early. |
| might / may have + past participle | maybe it happened (speculation) | The alert might have fired late. |
| must have + past participle | I'm sure it happened (deduction) | Recovery must have been exhausting. |
| can't have + past participle | I'm sure it didn't happen | Our Linux servers can't have crashed: only Windows machines were affected. |
| would have + past participle | the result in an imagined past | If the file had gone to a canary group first, fewer machines would have crashed. |
| needn't have + past participle | it happened, but it wasn't necessary | Lena needn't have woken half the team. |
| didn't need to + verb | it wasn't necessary (and usually it didn't happen) | Kestrel didn't need to fix anything: it wasn't affected. |
Must have or had to? Needn't have or didn't need to?
Must have means you're sure something happened; a past obligation is had to: I had to wake Lena. Needn't have says it was done for nothing: We needn't have restarted the cluster. Didn't need to only says it wasn't necessary; usually, it didn't happen either.
must have or had to?
must have + past participle: I'm sure (deduction)
- Look at the commit history. They must have worked all weekend.
- The errors began with the migration, so it must have caused them.
had to + verb: it was necessary (obligation)
- There was no automatic fix, so engineers had to delete the bad file machine by machine.
- Our runbook requires two people, so I had to wake Lena.
needn't have or didn't need to?
needn't have + past participle
- We needn't have restarted the cluster. (We did it, but it wasn't necessary.)
didn't need to + verb
- We didn't need to restart the cluster. (It wasn't necessary, and usually this means we didn't.)
Blameless, not blaming
A blameless postmortem aims modal perfects at the process, not at a person: The pipeline should have caught the change, rather than Rui should have tested the config. Questions like Who pushed this on a Friday? belong to the blaming side.
Blaming: about a person
- Rui should have tested the config.
- Who pushed this on a Friday?
Blameless: about the process
- The pipeline should have caught the change.
- The process let an untested change reach production.
Typical mistakes
The pipeline should of caught it.
The pipeline should have caught it.
should've sounds like "should of", but the word is always have.
The change should have went through a canary stage.
The change should have gone through a canary stage.
After have, use the past participle: gone, not went.
Yesterday I must stay late to fix the build.
Yesterday I had to stay late to fix the build.
Past obligation = had to. must have done = I'm sure it happened.
Yesterday I had deployed the fix and then I had gone home.
Yesterday I deployed the fix and then went home.
Events in order need the past simple, not the past perfect.
More lessons on this grammar: Modal verbs lessons and exercises · Past perfect lessons and exercises
Try the modal perfects exercises
Try them yourself: these are the same exercises your students do in edio.
What's in the lesson
- 11 auto-checked exercises
- 2 games
- 2 teacher-checked tasks
- 1 article
- 1 grammar scheme
- 1 set of word cards
- 1 audio clip
- 1 picture
- 1 transcript
The main objectives of this lesson are to:
- look back at a failure with modal perfects: The pipeline should have caught it. A canary stage could have stopped it.
- tell must have (I'm sure it happened) from had to (it was necessary), and needn't have from didn't need to
- tell an incident in order with narrative tenses: Tom was cooking dinner when his pager went off.
- write a blameless postmortem that criticizes the process, not a person: The process let an untested change reach production.
Lesson 6 of English for IT C1 · Across the Company closes unit 2, Shipping and incidents, the unit on estimates, releases and outages. It builds on the canary stages and rollbacks of lesson 5 and on the mixed conditionals of lesson 4, which return as would have; unit 3 then opens with a security advisory. Postmortems lean on should have, and a blameless one points it at the process.
Students spin a wheel of on-call war stories, then learn ten words such as mismatch, wildcard and page someone with pictures and audio, and match them to their closest meanings. A case study tells the outage: one configuration file, 78 minutes live, about 8.5 million Windows devices and a recovery that took days. In the AI-voiced listening, Lena and Tom discuss it at a postmortem reading club and compare it with their own team's config pushes. Four self-checking exercises follow the scheme, including a narrative-tense drill on last Thursday's incident and modal perfect gap-fills. In the speaking chapter, students explain the outage to Daniel without blame, then open boxes of incident questions.
Homework opens with a table of past simple and past participle forms and a sort of causes, impacts and recovery steps, which check themselves. Students then write the What went wrong section of a blameless postmortem and record an incident briefing for the next on-call engineer, both for the teacher to review.
- Grammar:
- narrative tenses · modal perfects · must have vs had to · needn't have vs didn't need to
- Topic:
- incidents · postmortems · CrowdStrike outage · deployment safety
Teaching tips
- Hold your own reading club: each learner brings a short public postmortem, retells it with narrative tenses, then judges it with two modal perfects about the process.
- Turn blame into process: write Who pushed this on a Friday? on the board, and pairs rewrite it blamelessly: The process let an untested change reach production.
- Draw the needn't pair as two timelines: on one, the team restarts the cluster for nothing (needn't have restarted); on the other, there is no restart (didn't need to restart).
- For in-company groups, use one of their own incidents, with names removed: learners tell it in order, then say what should have, could have and would have happened.
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The whole course: English for IT C1 · Across the Company
15 lessons at C1 for people who build software, in American English, with definitions instead of translations. The people of Kestrel Cloud, a fictional payments startup, write updates, reviews, RFCs and postmortems, explain tech to non-tech colleagues and negotiate scope. Real cases include the CrowdStrike outage and the xz backdoor.See the course
Unit 1 Talking to the team
async updates, code review and plain explanations: the future perfect, hedging, cleft sentences
Unit 2 Shipping and incidents
estimates, releases and outages: conditionals without if, phrasal verbs, modal perfects
Lesson 4Estimates, Deadlines and Saying No (Politely)Conditionals without if and mixed conditionals
Lesson 5Release Day: Rolling Out and Rolling BackPhrasal verbs and their noun forms
Lesson 6 · you're hereIncident! Learning from the CrowdStrike OutageModal perfects and narrative tenses
Unit 3 Security and design
advisories, trade-offs and RFCs: passive reporting structures, concession and contrast, nominalization
Unit 4 Docs, metrics and meetings
READMEs, dashboards and follow-ups: participle clauses, describing trends, reporting verbs
Unit 5 Retros, interviews and AI
looking back and ahead: wish and would rather, inversion, formal obligation and permission
