SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '44af6bc316855266037764ec686b828542b750e803cdf51706c524512ca90a16' 
  AND token = '5kUdSvIhVRT7oGPc7LSPp7uO5BNzexkvkTjIb8ULkm8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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