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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b255a36c30dce9016424e1900fe75a5553a5042a7170cb6c1ecc11ef0dde69ba' 
  AND token = 'RJzrLNcIDnJPsO9gw31Pm9ko6uO3P5j7/eXaxfaZEsU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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