SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f3934d3f3fe687fa151b201ee45f9980be4be03efc10975affd4044ef31a654' 
  AND token = '0FCOhowp1dfeNrXs2vrkBJBdIct1GPvJ0roIoMHgTDo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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