SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b616dc2d508644f67a53867b890577591cc3f2f6849f6e34dd02e5f05ca943dd' 
  AND token = 'PrytEycFhRoVnJ18lNjvuucmFRWnlDn98GCuz4OIlCM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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