SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c68603638d12cf0996af67317d0d7c1bf2209801cd8c345ea3ac761efe0051f7' 
  AND token = 'EvDHGuneErfXAaKqm8pHrsVzjOckRYYOCh+H322lX9g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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