SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e4abd18f206a1203bc854f788631199154f3bb0b892dbb447793869f6d8fac3' 
  AND token = 'TCuOWbH+Rb8rVCJoiDOg118OVmK3hk2GvrnWZoGzDp8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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