SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9425fb847115ca440dbc18b2a2718c5022318931499d9b018c4747eac851bbc' 
  AND token = '6DAVaGvzMT1HGp1jn9faYHOPRlKfLPFRk3WkPMh+j9Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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