SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2e249760e88b9d11fbf714797d82396560710bc8d828df67dca3b0df8ce35f0c' 
  AND token = 'z8J+Nv5EJOPXKN5QKnGWGgC4xAy2VkUcgBpVIt5N5+Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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