SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c523d66d67b1e21517618af2395449e88e71d55a1fd56daafd6019a9c7e9a275' 
  AND token = 'XiMx+yXXWGv6ZFON9/ujrdjrV9bkDJDXKdSM7EwjIi8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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