SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '375038165860699da79fe4f81729c8ecba3d5969ca5a5afb4006fc3ef839913b' 
  AND token = '6dnv1UUlQFNjjyZiHYFqLcph6qQVjBRduhHSkAhG6jE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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