SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '90d47af214670c48fc47485076d11d119842184c7f2e46becce08fb9c10ee8fb' 
  AND token = '+gWsWsvdQEbUHYNucJ3kBVfBjg+76DXpCtBh9kPiCMw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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