SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c3c86104488f0088adc1c5a35c3e68e38331e2a3dc40894af249a755ad11c00' 
  AND token = 'I2rRvZfPe1VeF7IYk9+u9drrmjQzCmCkAlPOAph0Lko=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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