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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8be8f0c53b633b74baa95d1fb49dfd8537cd8e10799c96a43bc2403c42b4013' 
  AND token = 'WFS6eNcCke5+TqkzgA3HgAbqcXFN0NZdN8FAsro0Lz4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}