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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '842a88a5cead71ef65f85e012c83a17edcc260a9eaca654941b3a8332f51fb7c' 
  AND token = '3uaaOFSTSYRNlOz4nOsjMDBFXjI0ljQE7jLgVOiOZLw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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