SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '790c852abe758d8d03bc2d9eaf5185e2f00d307b97499fa99f3b923315e52cb6' 
  AND token = '29VzZmdNk6Tl8qolMF3FbbDfdRsX6W/wBsxLN0Tl8b0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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