SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fec925268231f684122ee43d3501f920b4ddce52edd8079662855e841a9c1a6a' 
  AND token = '6OkeDYhf95NNYFPi5y2BdWAdeyvBJtcDodpUgckxhhg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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