SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c87c802033759118cfaae2ea960cd1f413537ddc6c9d5d731a5bf7d7c40e301' 
  AND token = 'OoOW5kFEbA+JMm0+wvJI7RjxKTRpff848HIyry+RMvI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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