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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ef793c1c631951fb30136b1288caaad36206d6a3d03e9bcc6f036c258c2fffc' 
  AND token = 'DfIg9KKkuNBlY8Aq7K2Kb1OQuMrpw3RgnrDkz/XK4c4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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