SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3d8b38e7c61aa11e79f3f04453ee0e1f8da5215c42cade78d97d6c5a9c4c86ff' 
  AND token = 'rDJvjwqKTho5+8UT+SCWAgtTPE+JJytEhAd3hyGWEOQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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