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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f9a5defcb1e1e0936977603abc076dd4300a3dc3a97ff8768772af8105b0ac4' 
  AND token = 'zCfCBgKgdJXvtZASz3r719OaLwJicj3dNDBTMrcl334=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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