SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5250e400f7ef6ebf6bce605e178f241dc59b92fc01759e70cfc2ae46565c3834' 
  AND token = 'yKlrSYQmzfKRJKfFIs6IHLLuZsgChcZl1yMMglJM4lc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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