SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6285d8f00849f2d299c1823265d71a6d0e6b53d046506204bb1a4dcbb08f71b' 
  AND token = 'MC1HQMKG3iwX1ltT2vsIhjV51+5d+TNj3ovtKin18So=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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