SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '908d7ffc6d858d8dea5d07c6a247fda6bd2de682deac701912e69675b38b9f09' 
  AND token = 'QRvGnKLuKI4e9D2fWqEGZCjaw5EXadlNdYzHqD0/xso=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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