SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dd76cdc367cc8f0b139a2241623c30541b1ab96274b966eefb8da3f4cf8a6931' 
  AND token = 'HQl4cuDp/a5/9jOZ5DX2LVhYHwKtGYxcReCqku82VLY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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