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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18f379f3d1937468f081e50b71fc38eedb1c351a94738e55b3355cbed990087a' 
  AND token = '/+v11EN4bPDg61EW2ysLyLpbHiBuWvaVeiDF1DzqyYM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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