SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56a06c398845773ad8623841608bc3879d06c8f0d4d18429f5cf72daa9a67f7f' 
  AND token = 'xvMLFpFLw40+q+MAW/SU5dK3+IKXv+ZyRllifG/xP4w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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