SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '256410ebbe78c7f3e351013d08596f56864ee2830fbb584f65ac37bddd85e076' 
  AND token = 'VbD0SCxN2RUPaky5Nl2IAQk/l+5J9bmEbLjnudTgumo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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