SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8a306207e43708ecef0cb2e7432a0827b5896d7f7f53133a9786a95710c9e33' 
  AND token = 'Z6AwRoLENObk/Y2n9I+5njjE4AZ56Cjqq7M1QxHopHk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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