SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '61d866175f2b79dcced760fa2a00520f0974e01334db1fffe07c74341a62edce' 
  AND token = 'cMMMdh4EKXuv4ns8XH0bGQs05NNMG4PVMLBDYPXHLlE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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