SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78c3c943024955b84f7b8bd793ecaf21707036116d8db100ed0728bb131f691a' 
  AND token = 'hunXiWtwRYWGmSlqWDM3cVZCusSTssHybFAWQi2DqXg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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