SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b372b2724fe5338b449f816fabd823479cfda1acfc095d0d20deb23e8ee2290c' 
  AND token = 'OK9uOwOcFBiRTzj0Xso8LB6y+7lapoq/Vc+Xov9KTB4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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