SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '140467f52a0767185f86abb817a3a363835457bd57df499ae15e8f8438a2d4f4' 
  AND token = 'NnquBqwDd1dnZh0e+lzMj3C+wnsq5oKVwX8c1+8/qNk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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