SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78dc50606416a058177a79468b923ae2e44bc36929d408e991cc8de6049b29c6' 
  AND token = 'uoiJzehjy1bhlNJPbpkSEYxHlLqWeKXOI5dgbil9PuM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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