SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c0557dc4f3c3e0fc343254c6471cd3abcb2866b7ade3d6727d9db249e18a14f5' 
  AND token = 'Re0v+YzSp5jYyKiFj5ZUJ9Dg7Da5nGMETLlkaVl74Y0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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