SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55eb3b8f24891f6390907ddebafec941ad273b17af1173702e8c4588acbc5c8c' 
  AND token = 'FlxVbrBhDfogMewdqpn+W/hduGYANoqV8P7zMgSABcI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00059

JSON explain

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