SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fda799960dee84814ee704fd0f090020cd05ecc220969a1649b887ef457659b9' 
  AND token = 'KSaU2uVH1LtBJfQdOtSlV5cEp1CW698P4LckSsOBm5g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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