SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '338f76de121ac1ecef74fc6fbfc583557909bfaf02e8fc86e7c565b03322004b' 
  AND token = 'QAxu9mPN9bSPODwbo9SyApXKmbmACpjv6DHvQkZSJHw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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