SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '981ee5c010d6de0514040359cd34df50233d66e93afd3cc5826d3240185f5625' 
  AND token = 'jT+EmldFuux3djEqgTVJnbWv7XSTM3WkrRerRYApysw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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