SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f21d7098405d5ff5dde4a222fe412d844e74afe982b2c30b9354cba1ecbe82f' 
  AND token = 'C2u7O8bmNuIx1x+NThDjLSP1slx1WJRDqDtLYlf+kcg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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