SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '721ea2cc6df781fea77bc8a51cd4f6454318b47612d7d8f840be7f08ad2760d7' 
  AND token = 'sl0l4WENp9dgBYtWOAJHS57qu5cblIXXtdtk5rDSvZs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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