Deployment Strategies

The deployment strategies are the ways the new version ships (L302) — the recreate (the old stopped, the new started: the downtime, the simple, L302), the rolling (the gradual replacement: the instances updated in batches, no downtime, L302), and the blue/green (the parallel environments: the green deployed, the traffic switched, the instant rollback, L302) — the selection (L302) by the downtime and the rollback the service needs (L302).

The one-sentence interview answer: "The deployment strategies are the ways the new version ships (L302). The recreate (L302): the old version stopped, the new started (L302) — the simplest (L302), the downtime (L302), the rollback (L304) is the redeploy of the old (L302). The rolling (L302): the instances updated in batches (L302) — the new and the old coexist (L302), no downtime (L302), the health checks (L295) gate each batch (L302), and the rollback (L304) rolls the batches back (L302). The blue/green (L302): the two parallel environments (L302) — the blue (the current, L302) and the green (the new, L302) — the green deployed and tested (L302), and the traffic (L273) switched (L302) — the instant rollback (L304): the switch back (L302). The selection (L302): by the downtime the service can take (L302) and the rollback it needs (L302) — the internal tool (L302) on the recreate (L302), the API (L233) on the rolling (L302) or the blue/green (L302). The AI shape (L173): the model update (L365) — the canary (L303) or the blue/green (L302) with the evals (L341) gating — and the code update (L296) — the rolling (L302) on the ECS (L295) with the health checks (L295) and the rollback (L304). The demo overwrites; the architect switches (L302)."

Think of the deployment strategies as the ways a store changes its menu. The recreate (L302): the store closes (the downtime, L302), the old menu removed (L302), the new menu posted (L302), the store reopens (L302) — simple, with the closed sign (L302). The rolling (L302): the store's counters (the instances, L302) switch one at a time (L302) — the line keeps moving (no downtime, L302), each counter's new menu checked (the health, L295) before the next (L302). The blue/green (L302): the store opens a second location (the green, L302) with the new menu (L302) — the customers (the traffic, L273) walk to the new door (the switch, L302) — and if the new menu flops (L302), they walk back (the instant rollback, L304). The store picks the way by the crowd (the downtime, L302) and the flop-risk (the rollback, L302).

   the menu change (the deployment, L302)
   ┌────────────────────────────────────────────────────────┐
   │ the recreate (L302) — the closed sign (the downtime)   │
   │ the rolling (L302) — the counters one at a time (L302) │
   │ the blue/green (L302) — the second location, the       │
   │ switch (L302)                                          │
   │ the pick (L302) — the downtime and the rollback (L302) │
   └────────────────────────────────────────────────────────┘

The mental model is the menu change: the closed sign, the counters, and the second location (L302).

   THE RECREATE (L302)          THE ROLLING (L302)
   old ── stop ──► new          [old][old][old]
   the downtime (L302)          [new][old][old] → the batches (L302)
                                [new][new][old] → the health gates (L295)
                                [new][new][new] → no downtime (L302)

   THE BLUE/GREEN (L302)
   the blue (the current, L302)  the green (the new, L302)
   the green deployed + tested (L302) → the traffic switched (L273)
   the rollback (L304): the switch back (L302) — instant (L302)

The flow is the three moves: recreate → rolling → blue/green (L302).

• The recreate (L302). The old stopped, the new started (L302): the simplest (L302), the downtime (L302), the rollback (L304) is the redeploy (L302).
• The rolling (L302). The instances updated in batches (L302): the new and the old coexist (L302), no downtime (L302), the health checks (L295) gate each batch (L302).
• The blue/green (L302). The two parallel environments (L302): the green deployed and tested (L302), the traffic (L273) switched (L302), the instant rollback (L304) — the switch back (L302).
• The selection (L302). By the downtime and the rollback (L302): the internal tool (L302) on the recreate (L302), the API (L233) on the rolling (L302) or the blue/green (L302).

• An AI API (L233). The rolling (L302) on the ECS (L295) — the batches (L302) with the health checks (L295).
• A model update (L365). The blue/green (L302) — the new model (L148) in the green (L302), the evals (L341) gating, the traffic (L273) switched (L302).
• An internal tool (L302). The recreate (L302) — the downtime (L302) acceptable (L302).
• A webhook consumer (L220). The rolling (L302) — the SQS (L270) consumer (L249) draining (L302) before the batch (L302).
• Anything shipped (L307). The L307 pipeline (L307) deploys with the strategy (L302) — the L302 move (L302) as the last mile (L307).

The through-line: the strategy is the deploy's move — the recreate, the rolling, or the blue/green (L302).

Say it in four moves:

1. The recreate. "The stop and the start — the downtime (L302)."
2. The rolling. "The batches — the gradual replacement, no downtime (L302)."
3. The blue/green. "The parallel environments and the switch (L302)."
4. The pick. "By the downtime and the rollback (L302)."

• The rollback is the strategy's shape (L302). The senior answer picks the strategy (L302) by the rollback (L304): the recreate's redeploy (L302), the rolling's batches (L302), the blue/green's switch (L304).
• The blue/green is the instant rollback (L302). The switch back (L304) — the seconds (L302), not the redeploy (L302).
• The rolling is the zero-downtime default (L302). The batches (L302) with the health gates (L295) — the API (L233) stays up (L302).
• The model is the risk (L365). The model update (L365) — the evals (L341) and the canary (L303) — the AI's change (L365) gated like the code's (L296).
• The state is the constraint (L302). The database schema (L268) — the strategy (L302) must handle the migrations (L268) — the blue/green (L302) with the compatible schema (L302).

• The overwrite (L302). The new version over the old (L302) — the rollback (L304) impossible (L302).
• The recreate for the users (L302). The downtime (L302) on the API (L233) — the rolling (L302) or the blue/green (L302) is the users' (L302).
• The blue/green with the schema break (L302). The incompatible migration (L268) — the green (L302) can't serve (L302); the backward-compatible schema (L268) is the fix (L302).
• The health gate missing (L302). The batch (L302) without the check (L295) — the broken version (L302) rolls on (L302).
• The strategy for everything (L302). The one move (L302) for every service (L302) — the pick (L302) is per service (L302).

• Pick by the downtime and the rollback (L302) — per service (L302).
• Gate the batches (L302) — the health checks (L295).
• Blue/green for the users' API (L302) — the instant rollback (L304).
• Handle the schema (L302) — the backward-compatible migrations (L268).
• Rehearse the rollback (L304) — the strategy's shape (L302).

Q: Walk me through the deployment strategies.

A: The three moves (L302). The recreate — the old stopped, the new started, the downtime (L302). The rolling — the batches, the gradual replacement, no downtime (L302). The blue/green — the parallel environments, the traffic switch (L302). The pick — by the downtime and the rollback (L302).

Q: How do you pick the strategy?

A: By two axes (L302): the downtime the service can take (L302) and the rollback it needs (L304). The internal tool (L302) — the recreate (L302). The users' API (L233) — the rolling (L302) or the blue/green (L302) — the instant rollback (L304).

Q: What's the blue/green?

A: The two parallel environments (L302): the blue — the current (L302); the green — the new (L302). The green is deployed and tested (L302), then the traffic (L273) switches (L302). The rollback (L304): the switch back (L302) — the instant (L302).

Q: How do you deploy a model update?

A: As the riskiest change (L365): the new model (L148) in the green (L302) or the canary (L303), the evals (L341) gating, and the traffic (L273) switched gradually (L303) — with the instant rollback (L304) to the previous model (L302).

• What's the recreate (L302)?
• What's the rolling (L302)?
• What's the blue/green (L302)?
• How do you pick (L302)?
• How do you deploy a model (L365)?

The senior read: the right columns for the users — the zero downtime and the instant rollback (L302).

// The deployment strategies (L302) — the ECS deployments (L295).
// THE RECREATE (L302) — the stop and the start (L302).
const recreate = {
  type: 'recreate',                          // the downtime (L302)
  // for the internal tools (L302)
};

// THE ROLLING (L302) — the batches with the health gates (L302).
const rolling = {
  type: 'rolling',
  minHealthyPercent: 50,                     // the batch size (L302)
  maxPercent: 200,                           // the old + the new (L302)
  healthCheck: '/health',                    // the gate (L295, L302)
};

// THE BLUE/GREEN (L302) — the parallel environments and the switch (L302).
const blueGreen = {
  type: 'blue-green',
  environments: { blue: 'current', green: 'new' },   // the two (L302)
  switch: 'traffic',                        // the Route 53 switch (L273, L302)
  rollback: 'switch-back',                  // the instant (L304)
};

// THE PICK (L302) — by the downtime and the rollback (L302):
//   the internal tool → the recreate (L302)
//   the API (L233) → the rolling (L302) or the blue/green (L302)
//   the model update (L365) → the blue/green (L302) + the evals (L341)

What the reader must SEE — the moves, declared:

  recreate + downtime       → the internal tool (L302)
  rolling + minHealthy 50   → the batches (L302)
  blue/green + switch       → the parallel environments (L302)
  switch-back               → the instant rollback (L304)
  the model update + evals  → the gated rollout (L365, L341)

  The pick by the downtime and the rollback (L302).

• The recreate is the simplest and the slowest (L302). The downtime (L302) — the internal tools' (L302).
• The rolling is the zero-downtime (L302). The batches (L302) — the capacity (L302) held by the min healthy (L302).
• The blue/green is the double cost (L285). The two environments (L302) — the capacity (L285) doubled during the switch (L302).
• The switch is the rollback's speed (L304). The traffic (L273) switched (L302) — the seconds (L302) to the previous version (L304).

• The deployment strategies = the deploy's moves (L302): the recreate, the rolling, the blue/green.
• The recreate: the stop and the start — the downtime (L302).
• The rolling: the batches — the gradual replacement, no downtime (L302).
• The blue/green: the parallel environments and the switch (L302).
• The pick: by the downtime and the rollback (L302).

DEPLOYMENT STRATEGIES = the ways the new version ships

THE RECREATE (L302)
  the old stopped, the new started (L302)
  the simplest (L302) · the downtime (L302)
  the rollback: the redeploy (L304)

THE ROLLING (L302)
  the instances in batches (L302)
  the new and the old coexist (L302) · no downtime (L302)
  the health gates (L295) · the rollback: the batches (L304)

THE BLUE/GREEN (L302)
  the blue (the current) + the green (the new) (L302)
  the green deployed + tested (L302) · the traffic switched (L273)
  the rollback: the switch back (L304) — instant (L302)

THE PICK (L302)
  by the downtime (L302) and the rollback (L304)
  the internal → the recreate (L302) · the API → the rolling (L302)
  or the blue/green (L302) · the model (L365) → the gated blue/green (L302)

INTERVIEW, 4 MOVES
  1 recreate "the stop and the start (L302)"
  2 rolling  "the batches, no downtime (L302)"
  3 blue/green "the parallel environments, the switch (L302)"
  4 pick     "by the downtime and the rollback (L302)"

You now hold the moves: the recreate, the rolling, and the blue/green — with the pick by the downtime and the rollback. The new version has its ways — and the menu is switched (L302).

Next: the 5% gate — Canary Deployments (L303).