SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '11f39ab98ad092ced730b525251bd2b98aff2d9a3c46ae9f1442693100d8e1ab' 
  AND token = '839emRVFijPfF35QuZFUFuQCqRYUOryyuPf07pmD/Gs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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