SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f7ad6742638ab856022d21ef34f9648964316b8833736989565dd5b896efd35' 
  AND token = 'YobHZshiAMBU/1L5hgj23fxB4+RcPxE+vfNRpkJ+mmg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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