SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '59fe680316a1fb7e3853dacc61aec5684a1cd23baebf775c0d9546331eb8da48' 
  AND token = 'B4aZbZLM9LuWs2nxblAmNAEvE1YCfdMStYMbnz4y5IQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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