SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '300fbba5f863291070ac163c997f79c68a5cb168750be91529a5992b432b07a1' 
  AND token = 'SLiUIAfODTNf0h9sDaGu3dKo593gGUCICBmXB7US438=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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