SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31555c9cc07f25cf746f66ebe9d636f621d04b5c5f8442b4a6d2ef9a2825a420' 
  AND token = 'xM6nh9iiYM0joswMlBMhqiEM/cE1EGAQa5+6EwUedq0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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