SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9aa64a644cac618818681ce73b4842c94f212a7bdcef3da188459c01a281edd' 
  AND token = 'lKQh0iTXpwkAI/uHNt1fiwU6gUHypnLC36eWMNL9D2E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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