SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a5271d128bf6d2f505b6bade4cb8c321ace262dd23d9b2f093f62d69d16c285' 
  AND token = 'xZBKJZJcoay0sMOuEAXf+xIp6rhdJttjdQYSHxwrDQA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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