SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39e7303e0eec480ba60e488197bf7d50c980559902a7f85d0809ea05e798781f' 
  AND token = 'rl75fE9KxZuGZ34bJL2KmPLuvneddOg+4X3bzELPTYY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}