SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b51f98a889e7aa2f0bf4ee19ad3fd735d910f574f359b9207cc3115291cc3dad' 
  AND token = 'b7GfOMjLDT6/qIM+rkYR74OwCKIpf/Vwi4t6jPyJNWw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}