SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a82eeea35864424625a14051029de18700a1eec93f8345f112b7c3a7e8e224d1' 
  AND token = 'JKhKKSAYzPdMoKerLgmUu0oIT2xoPSt4uVCE+U0pBFY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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