SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '38fffacd301ff19759e075f1594c115318265aac3fbac74f6af8417e520c9e85' 
  AND token = 'yRBW6w1KTTp4K1Zka5+gpScJkOfKvBqHafz/68UfZh4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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