SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0915238f6fe31e9cc45c6110185806ab3967a6fcfd3db0a7a50bcf80921a1278' 
  AND token = 'FkH7YtKOD+hDzjjivj1VzE4DoiDB1YhyMhpVmVs3jS4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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