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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c79d851fd46b598158b857efaa26fa08c73fc871c579e058fbef0f5565b1e0df' 
  AND token = 'CSfprqGNh4WiIlA8hxWSzZQ1gDq8mcaIE/gHRJDtScs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}