SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18a68faf066647ab060cb86cc0464588211817fff49886a0dad0d69a519b3c07' 
  AND token = 'iAWyCQs3pV+bAY1XRHuvvgME+RZ7H+HAMccK8ebtRhY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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