SDLC (Software Development Life Cycle)

The SDLC is the master pattern behind every way software gets built: a lifecycle from concept through requirements, design, build, test, deployment and maintenance. Every methodology you'll ever be pitched — Agile, waterfall, DevOps — is a strategy for executing these same phases. Knowing the pattern lets you read any vendor's delivery approach in one glance.

What It Is

The Software Development Life Cycle is the industry's structural model of how software is created and evolves: planning and requirements (what should exist and why), analysis and design (how it will work), implementation (writing the code), testing (proving it works), deployment (releasing it into use), and maintenance (fixing, updating, and eventually retiring it). Methodologies are execution strategies for this cycle: waterfall runs the phases sequentially with formal sign-offs between them; iterative approaches loop through them in short cycles; DevOps merges development and operations so the cycle runs continuously. The cycle never actually ends for living software — maintenance flows back into planning until retirement.

Why It Matters to You

The SDLC frame matters to you at two moments. In vendor selection, a vendor's SDLC maturity predicts delivery reliability more than their pitch does: ask how requirements changes are handled mid-cycle, what testing gate precedes deployment, and how production incidents feed back into planning — vague answers mark an organisation that runs on heroics. In governance, regulated industries expect a defined SDLC with evidence at each phase: requirements documents, test records, release approvals. 'We're agile' is not an SDLC; it is a scheduling strategy, and regulators do not accept it as a substitute for phase evidence.

When You'll Meet It

In vendor due diligence, project audits, and any conversation about how a system will be delivered or maintained. Make 'walk me through your SDLC' a standing interview question — the answer organises everything else a vendor will tell you.