SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7b1e7f00356d79072387bf2a9d1a94782395ee38b8d346c280ffdee70d930be' 
  AND token = 'df9Kvy2v5PXFlZpIe8PTFm+tHclxhUkMo7XvLiXgUuw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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