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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af8b5e5103dc70479e417f87a2d3c9f44428e2e5b22234c685ce43f0248c39c1' 
  AND token = 'AQdZzJhuGl5iexcKZXdnVGuwsOQsOmQTVc4JuyZNo5E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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