SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '612b8bd8904e99703b4879cc840826b1e1f1d2e2f4cf785dd39741ee35a2af19' 
  AND token = 'okvBzpyRgxEKzB2HAbxEGMG+cqdsHgMd2B/psbajfmU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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