SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd543d303cbbadc54dd6a2ff804486e14332b541045c0f1498ddff2d08bc43d57' 
  AND token = 'F255NolVijPBpxprDGBgukDMJlyf35WpJqqpuJyuL3c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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