Chapter 192: Flowcharts and Undercurrents

At 5:40 in the morning, Lin Chen woke on his own before the alarm went off.

Six hours of sleep put him exactly at the threshold of neural recovery. He opened his eyes. In the morning light, the water stains on the ceiling showed a gray-white pattern. A familiar dull ache rose from his left ankle, like a rusted gear slowly grinding between the bones. He threw back the blanket and sat up, gripping his calf with both hands and pressing upward from heel to knee. His muscles were stiff, the fascia tight, but the circulation was gradually returning. No complaints. Only procedure. Wash up. Splash cold water on his face. Change into loose pants to hide the slight limp in his gait. He left at 7:20. The subway was crowded; he held the rail and kept his weight to the right. The glass reflected his face—dark circles under his eyes, but his gaze was calm. At the office, he clocked in and powered up. The first thing he did was not answer email, but open the drawing software and pull up the finalized core flowchart from the night before.

Engineer Chen wanted the chart, not the PPT. That meant stripping away all decorative architectural packaging until only nodes, routes, timeout thresholds, and circuit-break conditions remained. He zoomed in on the call chain from the Order Center to the Inventory Service. Red dashed lines marked degradation paths; green solid lines marked the main flow. Beside each critical node, he added notes: Retry count ≤ 2, Timeout threshold: 800ms, Idempotency key: order_id + retry_seq. There was no magic in technology, only boundary conditions. He checked the dependencies one by one, changing synchronous calls on non-core links into asynchronous message queues to reduce coupling in the primary chain. Arrows crisscrossed the screen like an intricate vascular network. He had to make sure every branch had a way out.

At 12:30, he lined up in the cafeteria. He got one serving of stir-fried greens and half a portion of braised pork, then swiped his card. Sitting down, he opened his mobile banking app. Balance: 682.5. The registration fee for Wednesday's follow-up had already been deducted; estimated medicine costs were 120. He did the math: if the defense passed, the performance bonus would be paid on the fifteenth of the following month. That left a twenty-day cash-flow gap in between. In his hard-cover notebook he wrote: Emergency shortfall: 400. Source: credit-card installment / travel advance. Priority: low. If Friday's defense is rated A+, this can be covered.

The tip of his pen paused. He crossed out “travel advance” and replaced it with “overtime comp-time conversion.” No debt—that was the bottom line. Numbers were only units of measure. They carried no emotion. He closed the notebook and kept eating.

From two to five in the afternoon, he shut himself in a meeting room. The whiteboard filled with arrows and boxes. He simulated the extreme scenarios Engineer Chen might ask about: a datacenter power outage, cross-region sync delay, failure in primary-secondary database switchover. One by one, he matched them against the handling logic in his script. It was not memorization. It was deduction. He found a hidden risk: in the disaster-recovery simulation script, the refresh of the static fallback page cache depended on CDN preheating. If preheating failed, users would see an outdated campaign page after degradation kicked in. He revised the script at once, adding a local Nginx fallback configuration and setting the TTL to five minutes. The risk was compressed to an acceptable range. He saved the file and erased the whiteboard. Scraps of paper fell into the trash like an old shell being shed.

He got off work at 6:40. Transfer on the subway. The rush-hour crowd flowed like a slow river. He carried his laptop bag; his gait still held a slight limp, but the rhythm was steady. He got back to the rental at 7:20. Boiled noodles. Added an egg. After eating, he washed the dishes. At 7:50, he cleared the desk, leaving only a laptop, a hard-cover notebook, and a pen. He set his phone to silent and connected to the wired network. Wi-Fi was unstable; an online meeting was no place to gamble on probability. He poured himself a cup of warm water and set it by his hand. Then he adjusted his posture, back tight against the chair, left foot flat on the floor to avoid compressing the nerve.

At exactly eight, the internal messenger popped up the meeting link. He clicked in. The screen lit up, and Engineer Chen's face appeared in the upper right corner. Behind him was a conference room at headquarters, the whiteboard dense with formulas. No pleasantries.

“Send me the flowchart,” Engineer Chen said through the headset, his voice carrying a faint electrical hiss.

Lin Chen shared his screen. The PDF opened.

Engineer Chen said nothing for ten seconds. The mouse wheel scrolled. Zoom in. Zoom out.

“For degradation on the inventory service, you used local cache,” he said at last. “If the cache is penetrated, how does your script handle it?”

“A Bloom filter intercepts requests upfront. If there's no hit, it returns an empty result directly and doesn't penetrate through to the DB,” Lin Chen replied.

“What about the Bloom filter's false-positive rate?”

“Three per thousand. False positives go through the asynchronous compensation queue and do not block the main chain.”

“What if the compensation queue backs up?”

“If it exceeds ten thousand entries, it triggers an alert, and the degradation strategy switches to read-only mode. The front end displays a system maintenance notice. Preserve core transactions, discard non-core experience.”

Engineer Chen did not speak. On the screen, he picked up a pen and drew a circle on paper. “The logic closes. But your disaster-recovery simulation script is missing something.”

“What?”

“Rollback validation,” Engineer Chen said. “Degrading is easy. Recovery is hard. Your script only says how to switch to the backup link. It doesn't say how to switch back smoothly. Traffic during a major promotion comes in pulses. After the peak, if the primary chain hasn't fully recovered, a forced switchback will trigger a second avalanche.”

Lin Chen stared at the screen. His breathing slowed. He ran through the structure of the script in his head. It was true—he had assumed the primary link would switch back automatically after recovery, without building in a health observation window or gray-release return logic.

“Understood,” he said. “I'll add it tonight. A fifteen-minute observation window, then traffic switched back in stages at 10%, 30%, and 100%. If the switchback fails, it trips the circuit breaker automatically.”

“Right.” Engineer Chen nodded. “Technology isn't about who runs fastest. It's about who doesn't shatter when they fall. Old Chen will ask you this on Friday. Be ready with the answer.”

“Understood. Thank you, Engineer Chen.”

“No need. Get to work.” The connection cut off.

The screen went dark. The rental room fell quiet again. Lin Chen did not move at once. Leaning back in his chair, he closed his eyes. Engineer Chen's words were like a needle, puncturing the last layer of wishful thinking in his script. He opened his eyes, launched the code editor, created a new branch, and began writing the gray-release switchback logic. His fingers moved across the keyboard in a steady rhythm. No anxiety. Only execution. He introduced traffic-coloring tags, configured weighted routing, and wrote the health-probe script. Every line of code went through boundary testing.

At 11:20, the code was committed. The automated tests passed. In his hard-cover notebook he recorded: 20:00-23:20. Feedback from Engineer Chen. Added gray-release switchback and health observation window. Script V4.1 complete. Risk points closed.

He shut the notebook, stood up, and poured himself water. The pain in his left foot had worsened after sitting so long; one hand braced on the desk, he stretched slowly. The city lights outside the window were sparse. He took out his phone and sent his mother a text: The train ticket for Wednesday is booked. G1422, arriving at 8:15 a.m. I'll go to the station at 7 to meet you. After the follow-up, go straight to pick up the medicine. Don't wait in line.

Sent. The screen went dark.

He lay down. The water stains on the ceiling looked like a map. He thought of the dirt road in Qingshi Village, of the blood blisters rubbed onto his shoulders the first time he carried water, of the stars his younger brother Xiaoman used to draw on the backs of his exercise books. Those things had not disappeared. They had only changed form, pressing now against his spine. He could not collapse. If he did, there would be nothing left.

At 12:05 a.m., the phone vibrated.

Not his mother. An internal system alert:

[Monitoring Platform] CPU usage on Order Service Cluster Node 3 has spiked to 92% for 5 minutes. Auto-scaling has been triggered. Please confirm.

Lin Chen opened his eyes, sat up, turned on the computer, and logged into the monitoring backend. The graph showed that the peak had already receded. Auto-scaling had taken effect. But he noticed one detail: the traffic source that had triggered the expansion was not normal business traffic, but an unregistered crawler IP range.

He pulled up the access logs. IP geolocation: overseas. Request pattern: high-frequency scraping of product detail pages, with a forged User-Agent.

Not an attack. Data scraping. But the frequency was high enough to hit the resource threshold. If traffic from headquarters' stress test on Friday overlapped with this kind of abnormal scraping, the cost model for elastic scaling would be blown apart on the spot. What Old Chen wanted was control, not surprise spending.

He stared at the screen. The cursor blinked over the log file.

Tomorrow morning, he would need to write a traffic-scrubbing rule and submit it to the security team. At the same time, the cost estimate in the PPT would have to be tightened once more. He created a new document and typed the title: Abnormal Traffic Interception and Cost Hedging Plan. His pen left a clean, steady trail across the page. A problem had appeared. Solve it. One step at a time.

Outside the window, the neon still lit up one lamp after another, like silent coordinates marking the rhythm of the city's operation. He was only one gear inside it. But a gear, too, could bite into the drive shaft.