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This is an English adaptation of a Thai learning note based on “SDLC คืออะไร ?” by mikelopster. It preserves the source video, its core concepts, and the distinction between the presenter’s ideas and the added working prompts.

Contents
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The idea in one minute

The central idea

SDLC gives a team a shared map for deciding what to build, handing work across stages, finding problems early, and learning from the result.

Software that opens successfully is only one part of delivery. Teams also need to understand the user problem, design a solution, check it, release it, and learn from what happens after release. Together, these activities form the Software Development Life Cycle.

Know what to build

Agree on scope, expected quality, and what “done” means before implementation.

Know where a problem began

Use evidence from each stage to find the earliest point where a problem could have been caught.

Improve the next cycle

Bring outcomes and incidents back into the next plan.

THE CYCLE

Seven stages, one connected system

  1. Planning defines the problem, stakeholders, constraints, success measures, and risks.
  2. Requirements turn needs into behaviours and quality expectations that a team can check.
  3. Design compares feasible approaches, records trade-offs, and makes interfaces and data responsibilities clear.
  4. Implementation turns the design into working software in small, reviewable increments.
  5. Testing checks the important paths, edge cases, integrations, and acceptance criteria.
  6. Deployment releases a known version, verifies the result, and prepares a response if it fails.
  7. Operations and maintenance observes real use, resolves incidents, and feeds learning back into the plan.
What connects them

Every stage needs a clear input, a useful output, and a condition for handing work to the next stage.

WORKING RHYTHM

Choose a rhythm that matches the uncertainty

A sequential approach can help when requirements are stable and approvals are formal. Iteration is more useful when a team must learn from users or test an uncertain assumption. Incremental delivery works when a useful part of the system can reach people before the entire scope is complete.

Agile helps teams adapt to feedback. DevOps connects delivery with the work of operating a service. Neither removes the need for clear requirements, checks, or ownership.

AI WITH A CLEAR JOB

Use AI to examine each stage

SDLC gives AI a clearer job. Instead of asking for a generic answer, a team can ask it to expose ambiguity in requirements, compare design consequences, identify untested paths, or locate the stage where an incident should have been prevented.

Requirements: find what is still unclear

Here is a customer request: [paste the request] Separate it into system capabilities and quality expectations. Identify statements that are ambiguous or cannot yet be tested, and list the questions that must be answered. Do not propose an implementation or add assumptions for the customer.

Design: compare consequences

Given these requirements and constraints: [paste information] Propose feasible design options with benefits, costs, and trade-offs. Explain what each option is likely to make harder in six months. State what information is still missing before a decision.

Testing: find untested risk paths

Here are the requirements, code, and tests: [paste information] Identify paths that still lack tests and rank them by impact. Point out tests that may pass even when behaviour is wrong. Separate evidence from claims that still need an experiment.

Operations: feed the lesson back

Here is an incident timeline, impact, and evidence: [paste information] Explain which SDLC stage should have found this problem earlier. Propose a lasting addition to that stage and the cost of each proposal. State where the evidence is still insufficient.
PUT IT INTO PRACTICE

Start with one recurring pain

Choose a problem the team sees repeatedly: a feature that misses the need, a difficult release, or a handover that leaves the next person lost. Trace back to the stage that should have found it earlier, define the input, output, and exit condition for that stage, then try the change on one small cycle.

SOURCE & GLOSSARY

Source and terms

Source video: SDLC คืออะไร ? — mikelopster. The source is in Thai. This English version is an adaptation of the Thai learning note, not a verbatim transcript.

Acceptance criteria / Exit criteria

Acceptance criteria define whether a capability meets the expected need. Exit criteria define whether an activity is ready to pass into the next stage.

API contract / ADR

An API contract defines how systems exchange data and errors. An Architecture Decision Record captures context, a decision, and why it was made.

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