SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39839bbf7aa478d206a6abd0d2c3aa1ad61407d0d95b2259e76967a74f69ec50' 
  AND token = 'gSgekjIxV8+zGBuWV/e9+CpwVBZPpv9IdDwdrqgWqcw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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