SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b338452cebf661bfa04fcd1e5e8a1a60b316b2bb20fe884bc87bb38503029ec' 
  AND token = 'RU2qfPLozfnkGQcojHOWcK0SZkt6W9FFesAZJIlen5c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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