SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9beb756c3456ced476a5b49aa624073fec73a7ec366feebabb70a5cefdfcb391' 
  AND token = '17JtVR3WhXjIzKmAb9l47jFGyBEwIlC4+i81b4xyADI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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