SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42e4795b5b224d5773515a7eac411daf9afbadf98212861f530f9999a77ded87' 
  AND token = 'mdh6EcqzXFqpJHz0VxDUrgfpzkRC/5oPckyV9nxlQKU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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