SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e51175586cbbd813dec2a78e744a3634e17d85257076bcbd18b9d9948d485a67' 
  AND token = 'eJsjdMHADiIuvwrp5L5VzaU1euXe25ElNJy7dEnzrjw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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