SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b6cd4376d5e4829bb1f618d5a97e868564997fc364c759c6d1d8b94e890878a' 
  AND token = 't9RpQevEYPA9VBmCDByqGo+8z+YiHZrnDwuTat/oY+o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

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