SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3b311be3b344367aca24a5dc930f09f7443681dbc0e4c819e9a6182884c7f74' 
  AND token = 'FzzLUgTQXXxG6oUQBVi/ysZeMpodPvt2v2ELofqYMRw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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