SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a62d6f6ea6708717abe803ddc77264fa9bb8a7ee11e688c9a1a2e324e871827d' 
  AND token = '4SmFcUtu2bbC1nwlJjXLsXuCGQkDrLmH7cmZ2TnCjAM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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