SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c878ec8e31c262b1e3b6cced7528abf1044eb5d8db2a03230436810f836f90d0' 
  AND token = 'byuGCW1cgKaq2kVdwwH6Q69p1wT5EIUVFVaLek+4b2Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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