SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21c5dd339a14da6452389c7971098b9945b539b6626ff86554c8a9ed93508179' 
  AND token = 'fng9qlDyW/Mr8WD+RBDpCNIRoh6JktJzvxQBfRUKXrI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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