SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8f4bd5776bfaab473cdf83b37a8d551b9bb29c5213692e853221d3713a9838c' 
  AND token = 'q3G8lKsaPuX7Q+6DwLy91qY/ULsG+HnTbiHmlgD7hig=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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