SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d402e24f564b7db925c902d73e98951786cb9a03cdf26fe660158f231c1e99a' 
  AND token = 'rTTugTFzjj48kfU+5RiToipLX4m5ESMomPkifnq1MA8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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