SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6f15beafb20eeed9c714826d4a0d5787a699d0b7a977c63409ef800d7ce6671' 
  AND token = 'Fv/S/XwXp5Y8Gbkd6IK8//jN/L3Sq36Oh3l0wFF8Gzg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00059

JSON explain

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