SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '35fe86f98a3dd1528e74fe13002f1412821656836cb1620a97abd7e4c72487df' 
  AND token = 'UgQhrJWAMG1krfUWCNxfqztosfVL2hCCPqMY+mRDCPA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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