SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9d34c17b6acee2c3a40c57372acb68a70fb291bf251e14532d6517e45117a4f' 
  AND token = 'ylnLF2oPTvZ2vhZuKumJmtrinuZQ6LFjWzSP+Vm4vLQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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