SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e14be4244063c2528a4b9625a30003b71abe89605d790d44f4cfa6ab1388f465' 
  AND token = 'lORhMTIG2nDdXdQ2UBgv0BalsDrOkMh+jLmz/YunD98=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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