SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd8389a2030606e9562480849b97861b371759447257126b988652d2e0fcb1e5d' 
  AND token = 'qBAYgULE3f9D6zJORR2XnkV+2iznSbazMQUdwb41FoU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00069

JSON explain

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