SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2f37d78e4c2ed4ffe77036d696af8c5a9b37d2443a1bbb7feb4e59536747a1da' 
  AND token = '/fg+k3KhWNmsYMASXaXB5CUNXYmmUGgzRAsfiKzQVIY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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